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Inflammatory cytokines and acquired growth hormone resistance.

Resistance to growth hormone (GH)-mediated induction of insulin-like growth factor I (IGF-I) is a common complication of catabolic diseases, including critical illness and post-surgical conditions. This resistance to GH is believed to be permissive to the development of protein catabolism, cachexia and wasting, which are associated with an increased mortality rate. Data from in vitro studies and animal models suggest that increased levels of inflammatory cytokines can induce cachexia and might inhibit the effects of GH on target tissues. The molecular mechanisms involved are unclear, although an effect of cytokines on GH receptor signalling has been suggested. The GH-activated pathways that mediate the increase in IGF-I levels are not well understood, thereby impeding the elucidation of the effect of inflammatory cytokines. Several signalling cascades, like the JAK-STAT and MAP kinase pathways, have been shown to be activated by GH and some inflammatory cytokines, hence raising the possibility of crosstalk on this level. Our data, however, indicate that inflammatory cytokines have little or no effect on GH-mediated JAK-STAT signalling. In this review, we discuss these results and the possibility that secondary changes in the structure of chromatin are likely to be involved in the induction of IGF-I gene transcription by GH.

Animals↗

TNF-alpha is involved in activating DNA fragmentation in skeletal muscle.

Intraperitoneal administration of 100 microg kg(-1) (body weight) of tumour necrosis factor-alpha to rats for 8 consecutive days resulted in a significant decrease in protein content, which was concomitant with a reduction in DNA content. Interestingly, the protein/DNA ratio was unchanged in the skeletal muscle of the tumour necrosis factor-alpha-treated animals as compared with the non-treated controls. Analysis of muscle DNA fragmentation clearly showed enhanced laddering in the skeletal muscle of tumour necrosis factor-alpha-treated animals, suggesting an apoptotic phenomenon. In a different set of experiments, mice bearing a cachexia-inducing tumour (the Lewis lung carcinoma) showed an increase in muscle DNA fragmentation (9.8-fold) as compared with their non-tumour-bearing control counterparts as previously described. When gene-deficient mice for tumour necrosis factor-alpha receptor protein I were inoculated with Lewis lung carcinoma, they were also affected by DNA fragmentation; however the increase was only 2.1-fold. These results suggest that tumour necrosis factor-alpha partly mediates DNA fragmentation during experimental cancer-associated cachexia.

Animals↗

Development of an in-vitro model system to investigate the mechanism of muscle protein catabolism induced by proteolysis-inducing factor.

The mechanism of muscle protein catabolism induced by proteolysis-inducing factor, produced by cachexia-inducing murine and human tumours has been studied in vitro using C(2)C(12) myoblasts and myotubes. In both myoblasts and myotubes protein degradation was enhanced by proteolysis-inducing factor after 24 h incubation. In myoblasts this followed a bell-shaped dose-response curve with maximal effects at a proteolysis-inducing factor concentration between 2 and 4 nM, while in myotubes increased protein degradation was seen at all concentrations of proteolysis-inducing factor up to 10 nM, again with a maximum of 4 nM proteolysis-inducing factor. Protein degradation induced by proteolysis-inducing factor was completely attenuated in the presence of cycloheximide (1 microM), suggesting a requirement for new protein synthesis. In both myoblasts and myotubes protein degradation was accompanied by an increased expression of the alpha-type subunits of the 20S proteasome as well as functional activity of the proteasome, as determined by the 'chymotrypsin-like' enzyme activity. There was also an increased expression of the 19S regulatory complex as well as the ubiquitin-conjugating enzyme (E2(14k)), and in myotubes a decrease in myosin expression was seen with increasing concentrations of proteolysis-inducing factor. These results show that proteolysis-inducing factor co-ordinately upregulates both ubiquitin conjugation and proteasome activity in both myoblasts and myotubes and may play an important role in the muscle wasting seen in cancer cachexia.

Adenosine Triphosphatases↗

Role of lipid-mobilising factor (LMF) in protecting tumour cells from oxidative damage.

Lipid-mobilising factor (LMF) is produced by cachexia-inducing tumours and is involved in the degradation of adipose tissue, with increased oxidation of the released fatty acids through an induction of uncoupling protein (UCP) expression. Since UCP-2 is thought to be involved in the detoxification of free radicals if LMF induced UCP-2 expression in tumour cells, it might attenuate free radical toxicity. As a model system we have used MAC13 tumour cells, which do not produce LMF. Addition of LMF caused a concentration-dependent increase in UCP-2 expression, as determined by immunoblotting. This effect was attenuated by the beta3 antagonist SR59230A, suggesting that it was mediated through a beta3 adrenoreceptor. Co-incubation of LMF with MAC13 cells reduced the growth-inhibitory effects of bleomycin, paraquat and hydrogen peroxide, known to be free radical generators, but not chlorambucil, an alkylating agent. There was no effect of LMF alone on cellular proliferation. These results indicate that LMF antagonises the antiproliferative effect of agents working through a free radical mechanism, and may partly explain the unresponsiveness to the chemotherapy of cachexia-inducing tumours.

Adenocarcinoma↗

Medroxyprogesterone acetate inhibits interleukin 6 secretion from KPL-4 human breast cancer cells both in vitro and in vivo: a possible mechanism of the anticachectic effect.

Interleukin 6 (IL-6) is a multifunctional cytokine. Recent reports suggest that circulating IL-6 secreted from tumour cells plays an important role in cancer-induced cachexia. Medroxyprogesterone acetate (MPA) has been used as an endocrine therapeutic agent for patients with breast cancer. It has been suggested that MPA decreases serum IL-6 levels and preserves the bodyweight of patients with advanced breast cancer. However, the mechanisms of action responsible for the anticachectic effect of MPA have not been elucidated. Therefore, the effects of MPA on IL-6 secretion were studied both in vitro and in vivo using a human breast cancer cell line, KPL-4, which secretes IL-6 into medium and induces cachexia when injected into female nude mice. MPA (10-1000 nM) dose-dependently decreased basal IL-6 secretion into medium, and also suppressed tumour necrosis factor (TNF-alpha)-induced IL-6 secretion. Both basal and TNF-alpha-induced IL-6 mRNA levels were dose-dependently lowered by MPA. Moreover, intramuscular injections of MPA (100 mg kg(-1) twice a week) into nude mice bearing KPL-4 transplanted tumours significantly decreased serum IL-6 levels without affecting tumour growth and preserved the bodyweight of recipient mice. These findings suggest that suppression of IL-6 secretion from tumour cells, at least in part, causes the anticachectic effect of MPA.

Animals↗

Effect of a cachectic factor on carbohydrate metabolism and attenuation by eicosapentaenoic acid.

The effect of a proteolysis-inducing factor (PIF), produced by cachexia-inducing tumours on glucose utilization by different tissues and the effect of pretreatment with the polyunsaturated fatty acid eicosapentaenoic acid (EPA), has been determined using the 2-deoxyglucose tracer technique. Mice receiving PIF showed a profound depression of body weight (2.3 g) over a 24-h period, which was completely abolished by pretreatment with a monoclonal antibody to PIF or by 3 days pretreatment with EPA at 500 mg kg(-1). Animals receiving PIF exhibited a marked hypoglycaemia, which was effectively reversed by both antibody and EPA pretreatment. There was an increase in glucose utilization by brain, heart and brown fat, but a decrease by kidney, white fat, diaphragm and gastrocnemius muscle after administration of PIF. Changes in organ glucose consumption were attenuated by either monoclonal antibody, EPA, or both. There was a decrease in 2-deoxyglucose uptake by C2C12 myoblasts in vitro, which was attenuated by EPA. This suggests a direct effect of PIF on glucose uptake by skeletal muscle. These results suggest that in addition to a direct catabolic effect on skeletal muscle PIF has a profound effect on glucose utilization during cachexia.

Animals↗

Long-term effects of plasmid-mediated growth hormone releasing hormone in dogs.

Geriatric and cancer-afflicted patients often experience decreased quality of life with cachexia, anemia, anorexia, and decreased activity level. We have studied the possibility that a myogenic plasmid that expresses growth hormone releasing hormone (GHRH) can prevent and/or treat these conditions. We administered plasmid to 17 geriatric and five cancer-afflicted companion dogs with an average age of 10.5+/-1.0 and 11.3+/-0.6 years at enrollment, respectively. Effects of the treatment were documented for at least 180 days post-treatment, with 10 animals followed for more than 1 year post-treatment, on average 444+/-40 days. Treated dogs showed increased IGF-I levels, and increases in scores for weight, activity level, exercise tolerance, and appetite. No adverse effects associated with the GHRH plasmid treatment were found. Most importantly, the overall assessment of the quality of life of the treated animals increased. Hematological parameters such as red blood cell count, hematocrit, and hemoglobin concentrations were improved and maintained within their normal ranges. We conclude that intramuscular injection of a GHRH-expressing plasmid is both safe and capable of improving the quality of life in animals for an extended period of time in the context of aging and disease. The observed anabolic and hematological responses to a single dose of this plasmid treatment may also be beneficial in geriatric patients or patients with cancer-associated anemia and/or cachexia.

Aging↗

Changes in monoamine turnover in the brain of cachectic mice bearing colon-26 tumor cells.

Patients with cancer cachexia often suffer from psychiatric disorders. In the present study, we investigated the changes in monoaminergic activities in the brain in tumor-bearing mice with reference to the development of cachexia. Two clones, clone-5 (noncachectic clone) and clone-20 (cachectic clone), derived from the murine Colon-26 adenocarcinoma cell line (Nippon Roche Research Center), were inoculated subcutaneously at 1 x 10(6) cells/0.2 ml into the right lower back of BALB/c mice. In clone-20 mice, body weight and locomotor activity decreased significantly 10-15 days after tumor inoculation. The levels of noradrenaline, dopamine, and 3,4-dihydroxyphenylacetic acid showed no significant change among the three groups. The noradrenaline turnover rate in clone-20 mice was increased in cerebral cortex, hypothalamus, and midbrain. The 5-hydroxytryptamine turnover rate in clone-20 mice was increased in hippocampus, cerebral cortex, midbrain, and pons-medulla oblongata. In contrast, the dopamine turnover rate in clone-20 mice was decreased markedly in hippocampus, cerebral cortex, striatum, hypothalamus, and cerebellum. There was no significant change in amine turnover between control and clone-5 mice except for dopamine in hippocampus, cerebral cortex, and striatum and 5-hydroxytryptamine in striatum. No significant change in the levels of amino acids in the brain was observed among the three groups of mice. It is concluded that some of the psychiatric disorders from which cancer cachectic patients suffer might be ascribable to changes in monoaminergic activities in the brain.

Adenocarcinoma↗

A model that reproduces syndromes associated with human multiple myeloma in nonirradiated SCID mice.

A human myeloma line was used to create a model of human multiple myeloma in vivo that would reproduce the pathophysiology of the disease, including the cachexia associated with cancer. Unirradiated severe combined immunodeficient (SCID) mice were used as surrogate hosts for in vivo experiments that allowed the effects of autocrine (human) verus paracrine (murine) cytokines on the development of myeloma to be studied. Serum levels of human paraprotein increased over time and with the number of cells transplanted. Transplanted mice developed major syndromes, cachexia and paralysis (due to invasion of bones by myeloma cells), associated with multiple myeloma. Analyses of serum samples obtained from transplanted mice revealed that when the mice were terminal, total serum protein decreased on average by 20%, whereas serum triglycerides decreased on average by 50%. These data indicate the mice were cachectic, which was confirmed by necropsy. The mice had low but measurable levels of both human and murine interleukin (IL)-6, soluble IL-6 receptor, and murine IL-10 in their sera. The presence of these cytokines and the IL-6 receptor in sera are also characteristics of human myeloma in patients. Since human cells do not respond to murine IL-6, it was possible to demonstrate clearly the importance of autocrine IL-6 in establishing myeloma in situ. By reproducing both the hallmarks of a cancer as well as the accompanying paraneoplastic syndromes, this model should be useful in designing more effective therapies for both the primary cancer as well as the accompanying secondary diseases.

Animals↗

Hypothalamic appetite-regulating neuropeptide mRNA levels in cachectic nude mice bearing human tumor cells.

We previously reported that the human melanoma cell line, SEKI, induces severe weight loss in nude mice. In the present study, we examined the expression of weight-regulating neuropeptide mRNAs in the hypothalamus of this cancer cachectic model by using a sensitive quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method and in situ hybridization. mRNA levels of neuropeptide Y (NPY) and corticotropin-releasing hormone (CRH) in the whole hypothalamus were elevated significantly in the SEKI mice as compared with control mice. In situ hybridization showed that NPY and CRH mRNA were upregulated in the arcuate nucleus and the paraventricular nucleus, respectively. There were no significant differences in melanin-concentrating hormone (MCH), orexin (OX), and cholecystokinin mRNA levels between the SEKI and control mice. These results suggest that the NPYergic system is functioning in the rodent model of cancer cachexia; however, the role of the CRHergic system in energy homeostasis remains to be elucidated. This is the first report of the hypothalamic neuropeptide response to cachexia-inducing human cells.

Animals↗

Metabolic responses to tumour disease and progression: tumour-host interaction.

The progressive nutritional deterioration frequently found in cancer patients, is often referred to as cancer cachexia. In contrast to starvation, where it is possible to reverse the body composition changes by the provision of extra calories, in cancer cachexia this reversal is not observed, suggesting that anorexia alone is unlikely to be responsible for this wasting syndrome. Over the past decades a number of studies have focused on the possible mediators which may be responsible for metabolic abnormalities observed in cancer patients. Pro-inflammatory cytokines have been strongly implicated, but evidence supporting such a direct role is lacking. Recently, exciting work regarding molecules produced by tumour cells, and which may induce lipolysis and proteolysis, has been published. There is also evidence that increased metabolism of host resources may provide substrates which might promote tumour growth. A number of studies have demonstrated that polyunsaturated fatty acids, such as linoleic and arachidonic acid, are able to promote tumour cell growth either by directly stimulating mitosis or by inhibiting apoptosis. Even more interesting is the discovery of antagonists of these catabolic factors such as eicosapentanoic acid for the lipolytic factor, which may play a role in the treatment of these patients in the near future.

Cachexia↗

Weight loss in tumour-bearing mice is not associated with changes in resistin gene expression in white adipose tissue.

Resistin, a product of white adipose tissue, is postulated to induce insulin resistance in obesity and regulate adipocyte differentiation. The aim of this study was to examine resistin gene expression in adipose tissue from mice bearing the MAC16 adenocarcinoma, which induces cancer cachexia with marked wasting of adipose tissue and skeletal muscle mass. MAC16-bearing mice lost weight progressively over the period following tumour transplantation, while the weight of control mice remained stable. Leptin mRNA in gonadal fat was 50 % lower in MAC16 mice than in controls (p < 0.05). Plasma insulin concentrations were also significantly lower in the MAC16 group (p < 0.05). However, resistin mRNA level in gonadal fat in MAC16 mice was similar to controls (94 % of controls). Thus, despite severe weight loss and significant falls in leptin expression and insulin concentration, resistin gene expression appears unchanged in white adipose tissue of mice with MAC16 tumour. Maintenance of resistin production may help inhibit the formation of new adipocytes in cancer cachexia.

Adenocarcinoma↗

Nutritional deficiencies in patients receiving cancer chemotherapy.

Cancer often causes malnutrition and specific vitamin and protein deficiencies. Chemotherapy also causes deficiencies by promoting anorexia, stomatitis, and alimentary tract disturbances. Antimetabolite drugs in particular inhibit synthesis of essential vitamins, purines, and pyrimidines. Because vitamin levels in the blood are often nondiagnostic, nutritional deficiency is identified almost exclusively on the basis of clinical signs and symptoms and the patient's response to therapy. Signs and symptoms of cachexia and hypoalbuminemia are common in patients with advanced cancer. Deficiencies of vitamins B1, B2, and K and of niacin, folic acid, and thymine also may result from chemotherapy. Nutritional deficiencies are chemically correctable; however, the tumor must be eradicated to relieve cachexia.

Antineoplastic Agents↗

Response of hypothalamic NPY mRNAs to a negative energy balance is less sensitive in cachectic mice bearing human tumor cells.

We selected three human cancer cell lines [human melanoma (SEKI), human melanoma (G361), and human neuroepithelioma (NAGAI)] that have an ability to develop cancer cachexia syndrome with and without accompanying anorexia and examined the hypothalamic levels of mRNAs for neuropeptide Y (NPY), melanin-concentrating hormone, and orexin. The body weight of sham-operated mice continued to increase, while mice of all tumor-bearing groups lost weight. Competitive reverse transcription-polymerase chain reaction analysis showed that, regardless of feeding status, NPY mRNA levels were elevated in all tumor-bearing mice compared with sham-operated mice, although to a lesser degree than weight-matched pair-weight mice. Melanin-concentrating hormone and orexin mRNA in the hypothalamus followed the same pattern as NPY, although most of the differences did not reach statistical significance. These results support the notion that the response of NPY mRNA to a negative energy balance is less sensitive in these rodent models of cancer cachexia.

Animals↗

Lipid metabolism in cachectic tumor-bearing rats at different stages of tumor growth.

Rates of lipogenesis and lipoprotein lipase (LPL) activity were measured in liver, adipose tissue, heart, and tumor at several stages during 10 days of palpable growth of a transplantable Leydig cell tumor in rats. This model showed the same characteristics as human cancer cachexia, including anorexia, weight loss, and muscle wasting. Comparison with pair-fed controls showed that the rate of loss of body fat was greater than could be explained by anorexia alone. The rate of lipogenesis tended to decrease during the later stages of tumor growth, particularly in the liver, where there was a statistically significant reduction on Days 5 and 10. This may be largely attributable to decreased availability of substrates caused by decreasing food intake and increasing glucose uptake by the tumor. There was a significant decrease in plasma glucose concentration by Day 10. In contrast, LPL activity in adipose tissue was depressed from the earliest stage of tumor growth, and this is likely to be a major cause of lipid depletion in cancer. There was no difference in adipose tissue LPL activity between the fed and postabsorptive states in the tumor-bearing rats, indicating that the normal response to nutrient intake was impaired. Thus, treatment of cancer cachexia should concentrate on normalizing the metabolic response to nutrient ingestion.

Animals↗

Effect of acute acipimox administration on the rates of lipid and glycogen synthesis in cachectic tumor-bearing rats.

Increased energy expenditure in cancer cachexia may be associated with increased postprandial glycogen synthesis via an indirect pathway involving gluconeogenesis. The possible beneficial effect of acipimox, a nicotinic acid analogue that suppresses lipolysis and may also inhibit gluconeogenesis, were therefore examined. Rats bearing a transplantable Leydig cell tumor and freely fed controls were fasted overnight, then given a test meal with or without 10 mg of acipimox. The meal included 200 mg of [1-13C]glucose, and the rats were injected simultaneously with 7 mCi of 3H2O and 1 microCi of [14C]glycerol. The rats were killed one hour later. The rate of incorporation of 3H2O into hepatic glycogen was increased in the tumor-bearing rats and suppressed by acipimox. Positional analysis of the tritium incorporated into glycogen indicated that a greater proportion of the glycogen was synthesized via pyruvate in the tumor-bearing rats. Acipimox tended to reduce this proportion, although the effect was not statistically significant. Neither tumor growth nor acipimox significantly affected the proportion of 13C incorporated into different positions in the glycogen glucose. Glycogen synthesis from glycerol tended to decrease when lipolysis was suppressed by acipimox, although the statistical significance of this effect was marginal. Fatty acid synthesis in liver and adipose tissue was reduced in tumor-bearing rats, but acipimox had no effect. It is concluded that acipimox does suppress gluconeogenesis and glycogenesis in the postprandial state, but it does not normalize all the metabolic abnormalities observed in cancer cachexia.

Animals↗

Body composition analysis of cachectic rabbits by total body electrical conductivity.

A simple formula (1.536 x TOBEC + 475.146 = LBM, where TOBEC is total body electrical conductivity and LBM is lean body mass) to estimate LBM in grams was developed on the basis of the total body fat data obtained by ether extraction and TOBEC in normal rabbits. The formula was also applicable to rabbits with cachexia induced by inoculation of VX2 carcinoma or by starvation. We were able to assess the losses of body fat in the rabbits with cachexia at 10-day intervals by using TOBEC.

Animals↗

Elevated plasma cholecystokinin at high altitude: metabolic implications for the anorexia of acute mountain sickness.

The aims of the present study were to measure the satiety neuropeptide cholecystokinin (CCK) in humans at terrestrial high altitude to investigate its possible role in the pathophysiology of anorexia, cachexia, and acute mountain sickness (AMS). Nineteen male mountaineers aged 38 +/- 12 years participated in a 20 +/- 5 day trek to Mt. Kanchenjunga basecamp (BC) located at 5,100 m, where they remained for 7 +/- 5 days. Subjects were examined at rest and during a maximal exercise test at sea-level before/after the expedition (SL1/SL2) and during the BC sojourn. There was a mild increase in Lake Louise AMS score from 1.1 +/- 1.2 points at SL1 to 2.3 +/- 2.3 points by the end of the first day at BC (P < 0.05). A marked increase in resting plasma CCK was observed on the morning of the second day at BC relative to sea-level control values (62.9 +/- 42.2 pmol/L(-1) vs. SL1: 4.3 +/- 8.3 pmol/L(-1), P < 0.05 vs. SL2: 26.5 +/- 25.2 pmol/L(-1), P < 0.05). Maximal exercise increased CCK by 78.5 +/- 24.8 pmol/L(-1), (P < 0.05 vs. resting value) during the SL1 test and increased the plasma concentration of non-esterified fatty acids and glycerol at BC (P < 0.05 vs. SL1/SL2). The CCK response was not different in five subjects who presented with anorexia on Day 2 compared with those with a normal appetite. While there was no relationship between the increase in CCK and AMS score at BC, a more pronounced increase in resting CCK was observed in subjects with AMS (> or =3 points at the end of Day 1 at BC) compared with those without (+98.9 +/- 1.4 pmol/L(-1) vs. +67.6 +/- 37.2 pmol/L(-1), P < 0.05). Caloric intake remained remarkably low during the stay at BC (8.9 +/- 1.4 MJ.d(-1)) despite a progressive decrease in total body mass (-4.5 +/- 2.1 kg after 31 +/- 13 h at BC, P < 0.05 vs. SL1/SL2), which appeared to be due to a selective loss of torso adipose tissue. These findings suggest that the satiogenic effects of CCK may have contributed to the observed caloric deficit and subsequent cachexia at high altitude despite adequate availability of palatable foods. The metabolic implications of elevated CCK in AMS remain to be elucidated.

Adult↗