Cachexia of malignancy: potential role of insulin in nutritional management

Metabolomics in cancer research and emerging applications in clinical oncology

Cancer has myriad effects on metabolism that include both rewiring of intracellular metabolism to enable cancer cells to proliferate inappropriately and adapt to the tumor microenvironment, and changes in normal tissue metabolism. With the recognition that fluorodeoxyglucose-positron emission tomography imaging is an important tool for the management of many cancers, other metabolites in biological samples have been in the spotlight for cancer diagnosis, monitoring, and therapy. Metabolomics is the global analysis of small molecule metabolites that like other -omics technologies can provide critical information about the cancer state that are otherwise not apparent. Here, the authors review how cancer and cancer therapies interact with metabolism at the cellular and systemic levels. An overview of metabolomics is provided with a focus on currently available technologies and how they have been applied in the clinical and translational research setting. The authors also discuss how metabolomics could be further leveraged in the future to improve the management of patients with cancer.

New insights on the regulation of cancer cachexia by N-3 polyunsaturated fatty acids

Cancer cachexia is a multifactorial syndrome that develops during malignant tumor growth. Changes in plasma levels of several hormones and inflammatory factors result in an intense catabolic state, decreased activity of anabolic pathways, anorexia, and marked weight loss, leading to cachexia development and/or accentuation. Inflammatory mediators appear to be related to the control of a highly regulated process of muscle protein degradation that accelerates the process of cachexia. Several mediators have been postulated to participate in this process, including TNF-α, myostatin, and activated protein degradation pathways. Some interventional therapies have been proposed, including nutritional (dietary, omega-3 fatty acid supplementation), hormonal (insulin), pharmacological (clenbuterol), and nonpharmacological (physical exercise) therapies. Omega-3 (n-3) polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid, are recognized for their anti-inflammatory properties and have been used in therapeutic approaches to treat or attenuate cancer cachexia. In this review, we discuss recent findings on cellular and molecular mechanisms involved in inflammation in the cancer cachexia syndrome and the effectiveness of n-3 PUFAs to attenuate or prevent cancer cachexia.

Chronic exendin-4 treatment prevents the development of cancer cachexia symptoms in male rats bearing the Yoshida sarcoma

Cancer cachexia is the syndrome of weight loss, loss of appetite, and wasting of skeletal muscle and adipose tissue experienced by many individuals with cancer. Currently, few effective treatment and prevention strategies are available for these patients, due in part to a poor understanding of the mechanisms contributing to cachexia. Insulin resistance has been associated with cancer cachexia in epidemiological, human, and animal research. The present experiment was designed to examine the ability of Exendin-4, a GLP-1 agonist and insulin sensitizing agent, to prevent the development of cachexia symptoms in male Sprague Dawley rats bearing the Yoshida sarcoma. Following tumor implantation or sham surgery, rats were treated daily with saline or Exendin-4 (3 μg/kg body weight/day) and were monitored for tumor growth and cachexia symptoms for 21-23 days. As a result of large variability in treatment effects, data were analyzed separately for animals with large and small tumors. Exendin-4 treatment reduced tumor growth and prevented the development of cancer cachexia symptoms in animals with small, but not large, tumors. In addition, insulin levels were preserved in Exendin-4-treated tumor-bearing animals. The results of this experiment demonstrate a novel preventative therapy for cancer cachexia and a novel use of Exendin-4. Further research is necessary to determine the mechanisms through which Exendin-4 exerts these potent effects.

Palmitate turnover and its response to glucose infusion in weight-losing cancer patients

Palmitate turnover in weight-stable control subjects (n = 4) and weight-losing patients with progressive malignant disease (n = 4) has been determined. Measurements were made after an overnight fast and during glucose infusion (3.5 mg/kg/min). Turnover rates were calculated from plateau isotopic enrichment of palmitate in plasma during a continuous infusion of 1-13C palmitate. Palmitate turnover was higher in the cancer group before (180%) and during glucose loading (170%) compared with the control group. Palmitate turnover was reduced during glucose administration by approximately 34% in both groups. Plasma concentration of insulin was decreased and of cortisol was increased in the cancer group compared with the control group before and during glucose infusion. We conclude that cancer patients with weight loss have increased rates of fatty acid turnover indicative of enhanced mobilisation of body fat stores. Altered plasma concentrations of insulin and cortisol may mediate this effect. Nonetheless, even at more advanced stages of cachexia cancer patients have normal control mechanisms for inhibiting fatty acid turnover following administration of carbohydrate.

Effects of Chronic Lung Inflammation on Tryptophan Metabolism in Piglets

A fundamental question in animal nutrition is the amino acid requirement induced by inflammation and immune response. The aim of the present experiment was to study the effect of chronic lung inflammation induced by injection of complete Freund adjuvant on amino acid metabolism in pigs. For 10 days, we compared plasma haptoglobine and amino acid concentrations of piglets with chronic lung inflammation (CFA) with those of pair-fed littermate healthy pigs (CONTROL). Tryptophan was the only amino acid for which the plasma concentration was continously decreasing and did not reach the control level at the end of the experimental period. We suggested that an increase in tryptophan catabolism under indoleamine 2, 3 dioxygenase activation and/or tryptophan incorporation into acute phase protein could explained the decrease in plasma tryptophan concentration in pigs suffuring from chronic lung inflammation.

Tumor-Induced Changes In Host Metabolism: A Possible Role For Free Tryptophan As A Marker Of Neoplastic Disease

Tumor growth is associated with a number of metabolic abnormalities. Glucose metabolism is deranged as frequently revealed by an impaired oral glucose tolerance test. Lipoprotein lipase activity is depressed, resulting in hypertrigliceridemia after an exogenous lipid load. Also protein metabolism is deranged in cancer patients, as revealed by changes of plasma amino acid profile. Our previous studies on plasma amino acids have shown that increased plasma free tryptophan levels are a frequent finding in cancer patients. To sustain a possible role for free tryptophan as a marker of neoplastic disease, we measured its plasma concentrations in 241 patients with cancer. Plasma free tryptophan concentrations were found to be significantly elevated with respect to healthy controls in patients with breast, lung, colon, stomach, and cancer from various origin. The sensitivity of this marker in predicting the presence of the tumor was highest for stomach and lung cancer patients. High plasma free tryptophan concentrations seem to be directly related to the presence of the tumor, since in breast cancer patients they returned to within normal range after eradicative surgery.

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.

Cachexia and anorexia in malignancy

The cancer cachexia syndrome may be present in up to 80% of patients with cancer. Malnutrition resulting from cancer cachexia is a significant cause of morbidity and mortality. Anorexia, tissue wasting, and weight loss appear to be the result of metabolic abnormalities caused by host cytokine production in response to the tumor. The host cytokines include TNF-alpha, IL-1, IL-6, IFN-gamma, and D-factor. Nutritional support in the patient with cancer has been controversial, with the belief that tumor growth may be augmented; however, human studies fail to confirm that tumor growth occurs in excess of normal tissue growth. The efficacy of nutritional support in the cancer has not been adequately studied. Considerable interest exists in providing nutritional support pharmacologically to modify the response to malignancy.

Effects of insulin and insulin-like growth factors on protein and energy metabolism in tumour-bearing rats

The effects of insulin-like growth factor-1 (IGF-I), and a more potent variant LR3-IGF-I, which binds poorly to IGF-binding proteins, were investigated in rats bearing a mammary adenocarcinoma. The effect of insulin, either alone or in combination with LR3-IGF-I, was also investigated. Peptides were infused via osmotic minipumps for 6-7 days after tumour size reached 5% of body weight. Infusion of IGFs alone at either 200 or 500 microgram/day significantly decreased food intakes as well as circulating levels of insulin and glucose, and consequently failed to promote muscle protein accretion in the host. Tumour growth was increased by the IGFs, especially by LR3-IGF-I, even though these peptides did not promote growth of the adenocarcinoma in cell culture. Infusion of LR3-IGF-I, and to a lesser extent IGF-I, led to decreased rates of muscle protein synthesis and increased muscle protein breakdown, but each of these measures was closely related to the final tumour burden (r2 = 0.454 and 0.810 respectively; P < 0.01) and possibly resulted from a decrease in substrate supply to the host tissues. Insulin infusion (100 micrograms/day) increased food consumption by more than 50% and significantly decreased tumour growth. Insulin and LR3-IGF-I had a synergistic effect on host weight, which increased by 19.1 +/- 1.9, -1.1 +/- 4.7 and 37.9 +/- 1.5 g for insulin, LR3-IGF-I and combined treatments respectively. Carcass protein was increased by more than 10% with insulin treatment, due to increased rates of synthesis and decreased rates of muscle protein breakdown, but LR3-IGF-I had no positive effect on carcass protein accretion, either alone or in combination with insulin. Similarly, the amount of carcass fat was increased almost 2-fold by insulin treatment, whereas it was decreased by 30% by LR3-IGF-I. These changes may have arisen either from direct hormone effects on metabolism or from the indirect effects of food intake, or both. Our results suggest that IGF administration may exacerbate an insulin insufficiency associated with the tumour-bearing state and further decrease metabolic substrate supply to the host. This can be overcome by co-infusion of insulin.

Pharmacological interference with tissue hypercatabolism in tumour-bearing rats

Marked loss of body weight and profound waste of both skeletal muscle and white adipose tissue occur in rats into which the ascites hepatoma Yoshida AH-130 has been transplanted, associated with marked perturbations in the hormonal homoeostasis and the presence of circulating tumour necrosis factor and high plasma levels of prostaglandin E2 [Tessitore, Costelli and Baccino (1993) Br. J. Cancer 67, 15-23]. On the basis of previous findings, the present study examined whether the development of cachexia in this model system could be significantly affected by adrenalectomy or by pharmacological treatments that may interfere with proximal or distal mediators of tissue hypercatabolism. In no instance was tumour growth modified. Medroxyprogesterone acetate, an anabolic-hormone-like drug, was completely ineffective. In adrenalectomized animals, although changes such as the elevation of plasma triacylglycerols and corticosterone were corrected, the general course of cachexia was not modified. A partial prevention of muscle waste was observed with acetylsalicylic acid, a non-steroidal anti-inflammatory drug, or with leupeptin, a proteinase inhibitor. Insulin afforded the most significant preservation of muscle protein and adipose-tissue mass, which were maintained close to control values even 10 days after transplantation. The effects of insulin on gastrocnemius muscle and liver protein content were exerted by slowing down protein turnover, mainly enhancing synthesis. Consistently, the total free amino acid concentration in the gastrocnemius of insulin-treated rats 10 days after tumour transplantation was close to that of controls. Although treatment with insulin decreased plasma corticosterone to normal values, it did not modify the circulating level of tumour necrosis factor. On the whole these data show that it seems possible to prevent, at least in part, the tissue waste that characterizes cancer cachexia by purely pharmacological means.

In vivo effects of insulin on tumor and skeletal muscle glucose metabolism in patients with lymphoma

BACKGROUND

The anabolic properties of insulin have been suggested for use to reverse malnutrition associated with cancer. The host and tumor sensitivities to insulin are critical for such treatments, which aim to improve patient nutrition. The authors studied insulin effects on tumor and skeletal muscle metabolism with 2-[18F]-fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET).

METHODS

Six patients with lymphoma twice underwent [18F]FDG-PET imaging: once after fasting overnight and once during euglycemic hyperinsulinemic clamp. The dynamic uptake of the glucose analogue [18F]FDG was measured in diseased nodes and upper arm skeletal muscle in both metabolic states. The [18F]FDG uptake in muscle and the whole body glucose use during euglycemic hyperinsulinemic clamp were compared with those of weight-matched healthy subjects studied under similar circumstances.

RESULTS

In lymphomatous tissue, [18F]FDG uptake rates were similar in overnight fasting and euglycemic hyperinsulinemic clamp (38 +/- 10 versus 41 +/- 9 mumol/100 g/minute, not significant), whereas glucose uptake in skeletal muscle was increased by insulin (1.7 +/- 0.2 versus 3.8 +/- 0.5 mumol/100 g/minute, P = 0.012). Both basal (2.3 +/- 0.2 mumol/100 g/minute, P = 0.061) and insulin-stimulated (8.5 +/- 1.9 mumol/100 g/minute, P = 0.055) skeletal arm muscle glucose uptake rates were higher in control subjects than in patients. Whole body glucose use was 55% lower in patients than in control subjects (17 +/- 3 mumol/kg/minute versus 38 +/- 3 mumol/kg/minute, P = 0.002), consistent with insulin resistance in cancer.

CONCLUSIONS

We found that insulin does not induce major changes in glucose uptake of lymphomatous tissue. Although insulin sensitivity of skeletal muscle was also reduced in patients with lymphoma, the net insulin effect may counteract imbalance between glucose uptake of tumor and muscle, offering a potential means to circumvent at least some metabolic abnormalities found in cancer.

Homologous physiological effects of phenformin and chromium picolinate

The insulin-sensitizing drug phenformin, in addition to its clinical utility in type II diabetes, has been reported to lower blood lipids, reduce body fat, enhance cellular immunity, and--in rodents--to increase mean lifespan and retard the development of growth of cancer. Initial studies with the insulin-sensitizing nutrient chromium picolinate indicate that it aids glucose tolerance in type II diabetes, lowers elevated LDL cholesterol, reduces body fat while increasing lean mass, and--in rats--increases median lifespan. These effects are thus analogous to those reported for phenformin; chromium picolinate should be tested to determine whether it likewise has a favorable impact on cellular immunity and cancer risk. The ability of both phenformin and chromium picolinate to increase lifespan suggests that age-related insulin resistance may play a profound role in the aging process. It may not be coincidental that caloric restriction--the best documented technique for increasing lifespan--markedly increases insulin sensitivity. Safe, appropriate measures for promoting lifelong insulin sensitivity include a low-fat diet, exercise training, and supplemental chromium picolinate.

Effect of insulin-like growth factor 1 on host response to tumor

Oncology patients suffer multiple detrimental metabolic alterations. Among these are catabolism of tumor free body mass to supply nutrients to feed the tumor. This results not only in enhanced tumor growth but also poor wound healing and immunosuppression of the tumor host. Efforts are therefore being directed at finding methods for improving the nutritional status of the tumor host without enhancing tumor growth. We investigated the ability of two hormones, insulin-like growth factor-1 (IGF-1) and insulin, to improve physiologic function in tumor-bearing animals. Tumor-bearing animals received a continuous infusion of IGF-1 (2.20 mg/kg/day), insulin (820 microns/kg/day) or placebo via an osmotic minipump for 7 days. All animals were pair fed to eliminate nutritional intake as a variable. The placebo group lost 31.37 +/- 4.3 g of tumor free body mass during the study period. The insulin treated group lost 26.34 +/- 7.42 g and the IGF-1 group lost 5.07 +/- 3.25 g (P < 0.001, ANOVA). IGF-1 treatment failed to alter plasma glucose, lactate, or total amino acid concentration and failed to alter hepatic ketone body concentrations, but did improve hepatic mitochondria redox potential. Finally, IGF-1 improved splenic weight by 110% and splenic lymphocyte count by 300%. In conclusion IGF-1 appears to offer potential in supporting tumor free host body mass without stimulating tumor growth.

Nutritional and physiological consequences of tumour glycolysis

A frequent characteristic of many malignant tumours is an increase in anaerobic glycolysis, that is the conversion of glucose to lactate, when compared to normal tissues. The causes of this intensification involve changes in enzyme and glucose transporter levels, shifts of the isoenzyme patterns in the cancer cells to those similar to foetal tissues and a breakdown in the normal control mechanisms, most notably the Pasteur effect. The host must adapt, with a corresponding increase in gluconeogenesis. This change, along with other adaptations made by the host, eventually results in the syndrome known as cancer cachexia, which is characterized by anorexia and depletion and redistribution of the host energy stores. In some ways many malignant tumours behave much like parasites, drawing upon the host for nutrients such as glucose and returning waste products such as lactate to the host for recycling or disposal. This cycling of glucose and lactate between host and tumour has been the target for a number of proposed and tested treatments, with regard to the possible inhibition of tumour growth and/or possible prevention of some or all of the cachectic effects. Some of these suggested treatments have reached the point of clinical testing and show promise for continued research.

Perioperative nutrition in cancer patients

Cancer patients have the highest incidence of protein-calorie malnutrition seen in hospitalized patients, with significant malnutrition occurring in more than 30% of cancer patients undergoing major upper gastrointestinal procedures. Clinically significant malnutrition occurs as a result of diminished nutrient intake, increased nutrient losses, and tumor-induced derangements in host metabolism. In the absence of adequate exogenous nutrients, the body utilizes endogenous substrates to satisfy the ongoing requirements of both host and tumor for energy and protein. In those patients with malignant obstruction of the gastrointestinal tract, the tumor itself may induce diminished nutrient intake. Present day treatment modalities including gastrointestinal resection, chemotherapy, and radiotherapy compound these metabolic derangements, further increasing the risk of postoperative morbidity and death. The presence of malnutrition in cancer patients has prognostic importance. In a review of more than 3000 cancer patients, DeWys and colleagues identified significantly improved survival in those patients without weight loss compared with those had lost 6% of their body weight (Am J Med 69:491-497, 1980). Other investigators have noted increased postoperative morbidity and mortality associated with malnutrition. Early hypotheses suggested that reversal of weight loss would improve survival. The development and refinements of enteral and parenteral nutrition have provided the opportunity for studying the relationship between nutritional supplementation and postoperative prognosis. Nutrition support is therefore often instituted to improve nutritional status and thereby reduce the risks of postoperative complications. This article addresses the beneficial role of preoperative nutrition therapy in cancer patients.

The effect of insulin on glucose and protein metabolism in the forearm of cancer patients

This study was designed to study the effect of systemic hyperinsulinaemia (INS) on glucose and protein metabolism in cancer patients. Sixteen cancer patients (8 > 10% weight loss (WL); 8 < 10% weight loss (NWL)) were compared with 12 healthy controls. Glucose uptake (GU) and phenylalanine (PHE) exchange kinetics were measured across the forearm in the postabsorptive state (PA) and in response to INS (71 +/- 5 microU ml-1). At steady state in response to INS, the negative PA PHE net balance became significantly positive, and GU significantly increased, for cancer and control groups, with no significant differences between the two groups. Subset analysis of NWL cancer vs. WL cancer found no difference between WL and NWL for the change in PHE balance from PA and INS, however GU increased significantly only for the NWL group between PA and INS. These data indicate that cancer patients are not resistant to the anabolic effect of INS on protein metabolism, regardless of weight loss, but are resistant to the effect of INS on glucose metabolism when further along in the disease process as evident by more significant weight loss. This differential response to the effect of INS can be exploited in an attempt to promote protein accrual in weight-losing cancer patients.

A review of cancer cachexia and abnormal glucose metabolism in humans with cancer

In 1919, glucose intolerance became the earliest recognized metabolic abnormality in cancer patients. Prior to the development of severe malnutrition, colon, gastric, sarcoma, endometrial, prostate, localized head, neck, and lung cancer patients had many of the metabolic abnormalities of type II (noninsulin dependent) diabetes mellitus. These metabolic abnormalities include glucose intolerance, an increase in both hepatic glucose production (HGP) and glucose recycling, and insulin resistance. In a study of over 600 cancer patients, a diabetic pattern of glucose tolerance test was noted in over one-third of the patients. An increased rate of HGP, commonly seen in diabetics, has been noted in almost all types of cancer patients studied to date. Etiology of the increased glucose production in the cancer patient is not known, but abnormalities in the counter regulatory hormones, especially growth hormone, may contribute to the development of abnormal glucose metabolism. A second possible stimulus for the increase in HGP could be the glucose needs of the tumor. Abnormally high glucose utilization rates in small amounts of tumor tissue have recently been described. This suggests that small tumors may have large needs for glucose calories. An increase in anaerobic glycolysis in the tumor tissue can increase lactate production in the tumor-bearing human, thus supplying substrate to the liver to increase glucose production rates. In this paper, the nature of abnormal glucose metabolism in cancer patients is described.

Cancer cachexia is transmissible in plasma

The cause of cancer cachexia is unclear. Tumors may be competing with the host for ingested nutrients or may be releasing some factor that actively inhibits energy utilization. To explore these questions, plasma was sterilely collected and pooled from 103 terminally cachectic Fischer 344 rats implanted with an experimental sarcoma. Control plasma was collected in similar fashion from 138 nontumor-bearing rats (NTBP). Plasma from tumor-bearing rats (TBP) or NTBP was continuously infused in a randomized, blinded fashion for 4 days into 20 normal rats. During infusion, food intake and nitrogen excretion were measured daily. At sacrifice, body weight and organ masses were determined. Rats receiving TBP demonstrated an immediate and profound anorexia compared with those receiving NTBP. Total food intake during treatment was 31.2 +/- 3.3 (g +/- SEM) in the TBP group versus 48.2 +/- 2.8 in the NTBP group (P less than 0.001 by t test). Likewise, the total decline in body weight was greater in the TBP group as compared with the NTBP group (-35.2 +/- 3.4 versus -14.6 +/- 4.0, P less than 0.001). Mean daily nitrogen balance during treatment was negative in the rats receiving TBP (-14.5 +/- 20.1 mg +/- SEM) while remaining highly positive in the rats receiving NTBP (110.7 +/- 19.3, P less than 0.002). Finally, cardiac and gastrocnemius muscle masses were decreased, while hepatic mass was unaffected. These data demonstrate that the syndrome of cancer-associated cachexia is transmissible in plasma and therefore may be mediated by a circulating molecule or molecules. Identification and purification of the molecule(s) responsible for this effect would have obvious clinical benefits.

Effects of chemotherapy and remission on carbohydrate metabolism in dogs with lymphoma

After a 12-hour fast, blood samples were obtained from 27 dogs with previously untreated lymphoma before and 5, 15, 30, 45, and 60 minutes after an intravenous (IV) challenge with 500 mg/kg dextrose. This procedure was done for each dog before up to five treatments with the IV doxorubicin (30 mg/m2 every 3 weeks). All dogs achieved a complete remission. Samples were assayed for glucose, lactate, and insulin concentrations, and results were compared statistically with those from 16 normal control dogs of similar weight and age undergoing an identical dextrose challenge before and 3 weeks after receiving one dose of IV doxorubicin (30 mg/m2). Glucose, lactate, and insulin concentrations did not change significantly in response to glucose challenge in control dogs after doxorubicin chemotherapy. Lactate and insulin concentrations in untreated dogs with lymphoma were significantly higher than controls. This hyperlactatemia and hyperinsulinemia did not improve when dogs with lymphoma were put into remission with doxorubicin chemotherapy. The results indicate that carbohydrate metabolism is altered in dogs with lymphoma, and that these abnormalities do not improve when a complete remission is obtained with doxorubicin chemotherapy.

Clenbuterol treatment increases muscle mass and protein content of tumor-bearing rats maintained on total parenteral nutrition

Treatment of tumor-bearing (TB) and control rats with the anabolic beta-2 agonist drug clenbuterol (CLE) for 14 days reduced food intake for 4 days initially. Feeding was increased in anorectic TB rats, however, during the last 7 days of drug administration. Since minimal muscle savings were observed in chow-fed TB rats treated with CLE, the anabolic effects of this drug were investigated in a second experiment on TB rats maintained on total parenteral nutrition (TPN). Sixteen days after the subcutaneous transplantation of methylcholanthrene-induced sarcomas rats was begun on a 2-week schedule of TPN. One group of these rats was treated daily for 14 days with CLE, while the remaining rats received injections of saline. Additional groups of TB and nonTB rats were maintained on rat chow for this period and treated with saline. Although TB rats maintained on rat chow or TPN and treated with saline exhibited significantly decreased gastrocnemius muscle weight and protein content, treatment of TB-TPN rats with clenbuterol normalized muscle mass and increased muscle protein content significantly and increased plasma concentrations of branched-chain amino acids. These results indicate that although nutritional support of TB organisms does not result in protein repletion, the addition of an anabolic drug renders the nutritional support highly efficacious.

Hormonal factors associated with weight loss in patients with advanced breast cancer

Fasting blood samples were collected from 83 patients with histologically proven breast cancer and analysed for plasma glucagon, serum immunoreactive tumour necrosis factor (TNF alpha), insulin, glucose, growth hormone, cortisol and TSH. Samples from patients with known diabetes mellitus or thyroid disease, and those on parenteral nutrition or with evidence of infection were excluded as were patients who had a history of weight loss through dieting or who were anorexic. Fasting plasma glucagon, serum cortisol and immunoreactive TNF alpha concentrations in patients with stage IV breast cancer who had developed weight loss were significantly higher than those in patients with stage IV disease who had not developed weight loss. There were no significant differences in the fasting serum concentrations of insulin, glucose, growth hormone and TSH between the two patient groups. The association between weight loss in stage IV breast cancer and increased concentrations of plasma glucagon, serum cortisol and TNF alpha suggests a possible role for these hormonal factors in the development of cancer cachexia.

Insulin action and metabolism in patients with head and neck cancer

Cachexia is a phenomenon commonly observed in patients with cancer, but its etiology is poorly understood. Abnormalities of insulin action and metabolism that have been hypothesized to promote cancer cachexia were investigated in this study using a computerized euglycemic clamp and modified frequently sampled intravenous glucose tolerance test (FSIGT) in a group of malnourished patients with localized head and neck cancer, and in healthy, well-nourished, age- and, sex-matched controls. Glucose disposal rates, determined by the euglycemic clamp at three different rates of insulin infusion did not differ significantly between the two groups. However, mean plasma insulin concentrations at each level of insulin infused were significantly lower in the patients with cancer than in the control subjects resulting in unexpectedly higher calculated insulin metabolic clearance rate in the patients with cancer. Peripheral insulin sensitivity calculated from the slope of glucose disposal versus plasma insulin concentration did not differ between the two groups. Results from the FSIGT demonstrated no difference in insulin sensitivity or insulin-independent glucose disappearance between the two groups. However, whole body glucose appearance was significantly elevated in the patients with cancer. Thus, increased whole body glucose utilization in the absence of insulin resistance or increased insulin-dependent glucose disposal was observed. These data are consistent with the concept of a localized tumor acting as a glucose drain in which case increased glucose appearance and increased insulin clearance would defend against hypoglycemia.

Nutritional support of patients with cancer of the gastrointestinal tract

Malnutrition is extremely common in patients with malignant disease. Whereas the causes are multifactorial, the predominant factor is the imbalance between nutrient intake and host nutrient requirements. Furthermore, the evidence suggests that cachexia is related to abnormal changes in host intermediary metabolism induced by host-tumor interactions, and endogenous peptides such as TNF may be important mediators. The role of nutritional therapy in cancer patients remains to be defined. Clearly, patients with severe malnutrition benefit from nutritional intervention. However, the benefit of nutritional therapy in less severe cases of malnutrition as an adjuvant to oncologic therapy has yet to be established.

Cancer cachexia

Cancer cachexia has been listed as a major cause of death in cancer patients. In order to investigate the metabolic effects of the tumor on the host, we have evaluated an experimental model of cancer cachexia in the mouse (MAC16 colon adenocarcinoma), in which weight loss can reach 30-40% of initial weight with a tumor burden of only 2.5%, without a reduction in the intake of either food or water. The weight loss appears not to arise from tumor necrosis factor production, which is associated with a marked reduction in both food and water intake, but may be a result of catabolic factors produced by the tumor and present in the circulation. Both insulin and 3-hydroxybutyrate are effective inhibitors of the tumor catabolic factors in vitro and protect, to some extent, weight loss in vivo. However, whereas 3-hydroxybutyrate was associated with a reduction in tumor weight, insulin caused an enhancement, suggesting that the former may be more appropriate than the latter in the clinical treatment of cancer cachexia.

Metabolic effects of cancer

The potential causes of deranged metabolism in cancer are discussed with emphasis on changes in energy metabolism of glucose, fat and protein. The implications of these changes for the treatment of cachexia are then considered.

Reversal of the toxic effects of cachectin by concurrent insulin administration

Rats treated with recombinant human tumor necrosis factor-cachectin, 100 micrograms/kg ip twice daily for 5 consecutive days, had a 56% decrease in food intake, a 54% decrease in nitrogen balance, and a 23-g decrease in body weight gain vs. saline-treated controls. Concurrent neutral protamine hagedorn insulin administration of 2 U/100 g sc twice daily reversed all of these changes to control levels without causing any treatment deaths. The improvement seen with insulin was dose independent. Five days of cachectin treatment caused a severe interstitial pneumonitis, periportal inflammation in the liver, and an increase in wet organ weight in the heart, lungs, kidney, and spleen. Concurrent insulin treatment led to near total reversal of these histopathologic changes. Cachectin treatment did not significantly change blood glucose levels from control values of 130-140 mg/dl, but insulin plus cachectin caused a significant decrease in blood glucose from 1 through 12 h after injection. Administration of high-dose insulin can near totally reverse the nutritional and histopathologic toxicity of sublethal doses of cachectin in rats.

Effect of insulin on weight loss and tumour growth in a cachexia model

A comparison has been made between the effects of daily insulin injection and a ketogenic diet on weight loss and tumour weight in an experimental model of cancer cachexia (MAC16). Weight loss associated with the MAC16 tumour was significantly reduced both by a ketogenic diet (80% MCT) and by daily insulin injections without an increase in either food or water consumption. Animals fed the 80% MCT diet had a significantly reduced tumour weight compared with controls fed a normal laboratory diet, while in animals administered 20 U insulin kg-1 day-1 the tumour weight was 50% greater than in saline infused controls. The stimulation of tumour growth by insulin was counteracted by the inclusion of 3-hydroxybutyrate in the drinking water without any alteration in the extent of weight loss. Depletion of both carcass fat and muscle dry weight in animals bearing the MAC16 tumour was reversed in animals administered either insulin or an 80% MCT diet. Animals bearing the MAC16 tumour had a reduced nitrogen balance compared with non-tumour-bearing controls, mainly due to excess urea excretion, and this was reversed towards control values in animals fed an 80% MCT diet, but not in animals administered insulin. These results suggest that a ketogenic diet is more effective than insulin administration in reversing the cachectic process and has the advantage of a concomitant reduction in tumour weight.

Geriatric nutrition

In recent decades, veterinary medicine has become more successful in prolonging the healthy, useful lives of pets. As a result, the practitioner spends a greater part of each practice day caring for the geriatric animal, both healthy and unhealthy. Because of their longevity, older pets are typically regular family members, with owners who seek the finest health care possible for their pets. The practice of geriatric medicine most properly should begin not when the dog or cat reaches some specific "golden" age, but rather when the wiggly, robust puppy or kitten receives its first examination. Like all parts of a sound preventive program, geriatric nutrition best follows from a well-considered juvenile and adult nutrition program. Furthermore, once it becomes senior, the "well" geriatric is as much a candidate for a diet designed especially to accommodate old age changes as is his unhealthy contemporary. In fact, evidence suggests that appropriate dietary management of the healthy, but often subclinical, patient may help postpone the signs of dysfunction and increase quality and length of life. A knowledge of the most significant nutrients and the impact of each on aging systems is now, and will become increasingly more, important to the progressive, skillful veterinarian.

Insulin and acivicin improve host nutrition and prevent tumor growth during total parenteral nutrition

The effect that a 14-day treatment program of total parenteral nutrition (TPN) combined with the glutamine antimetabolite, acivicin, and anabolic hormone, insulin, has on carcass weight and muscle sparing was investigated in tumor-bearing rats. Although TPN resulted in increased carcass weight gain as compared to chow-fed tumor-bearing rats, no savings in gastrocnemius muscle could be demonstrated. The combination of TPN with daily insulin treatment elicited significant increases in both carcass weight and muscle savings, with no alteration in tumor growth. Although combining acivicin with TPN halted tumor growth and increased carcass weight, the change in carcass weight was less than that observed with the insulin-TPN combination. No muscle savings were observed in the acivicin-TPN-treated rats. Yet when acivicin and insulin were combined with TPN, tumor growth was stopped, carcass weight was gained, and muscle mass was saved. Therefore, these experiments suggest that it is possible to add lean body tissue and stabilize tumor growth in rats that receive TPN through anabolic hormone treatment combined with an inhibitor of tumor metabolism.

Recombinant human tumor necrosis factor induces acute reductions in food intake and body weight in mice

We examined the effects of treatment with rHuTNF on food consumption and body weight in C3H/HeJ mice. rHuTNF was administered intraperitoneally either by injections of 3, 12, or 24 micrograms twice a day or by implantation of osmotic pumps that released 0.75, 3, or 12 micrograms per day. Dose-dependent reductions in both food intake and weight were induced by rHuTNF. However, in spite of continued exposure to rHuTNF, the mice developed a resistance to rHuTNF and resumed their pretreatment food intake and weight. Non-immunological factors may play a role in the development of this tolerance, since it developed rapidly and faded within 2 wk of cessation of exposure to rHuTNF.

Insulin resistance in patients with colorectal cancer

The euglycaemic glucose clamp technique has been used to assess insulin resistance in patients with colorectal adenocarcinoma. Ten cancer patients were studied and compared with control subjects matched for age, sex and nutritional status. Forty-one euglycaemic clamps were performed at one of five different insulin infusion rates (20, 30, 40, 100 or 200 milliunits min-1 m-2). Glucose disposal was significantly decreased in the cancer group at all insulin infusion rates, whilst attained insulin levels and metabolic clearance rates of insulin were comparable in the control and cancer groups. Analysis of dose-response data allowed assessment of sensitivity (insulin concentration of half maximal glucose disposal) and responsiveness (maximal glucose disposal). Responsiveness was significantly reduced in the cancer group (40.3 versus 71.5 mumol kg-1 min-1; P less than 0.001), whilst sensitivity was similar (93.7 milliunits l-1 in controls versus 90.8 milliunits l-1 in cancer patients), suggesting a postreceptor defect in insulin action in the cancer group.

Tumors secreting human TNF/cachectin induce cachexia in mice

Anorexia and weight loss are serious complications that adversely effect the prognosis of cancer patients. It has been suggested that TNF/cachectin may cause cachexia. To determine if TNF/cachectin can induce progressive weight loss in tumor-bearing animals, a clone of the human TNF/cachectin gene was isolated and inserted into a mammalian expression vector. This construct was transfected into CHO cells, and a cell line (CHO/TNF-20) that secretes TNF/cachectin was isolated. A cell line (CHO/CMV-Neo) that contains the same expression vector without the TNF/cachectin gene was also isolated. Nude mice injected intraperitoneally with CHO/TNF-20 cells died more quickly than mice injected with CHO/CMV-Neo cells. Eighty-seven percent of mice inoculated intramuscularly with CHO/TNF-20 cells developed severe cachexia and weight loss. All mice bearing CHO/CMV-Neo tumors maintained or increased their body weight. We conclude that mice bearing tumors that secrete TNF/cachectin develop progressive wasting and die more quickly than mice bearing control tumors.

[Changes in nutritional status at the initial phase of treatment of cancers and malignant hemopathies]

Changes in nutritional status at the initial phase of treatment of cancers and malignant blood diseases were evaluated in 32 male patients (mean age 58 +/- 18 years) examined during three 4-day stays in hospital (T0, T1, T2) at 2 months' interval. On the first day of each stay the following parameters were measured: food intake (kcal/day), weight (kg), squared height (m), fat mass (kg) obtained by measuring 4 skin folds and using Durnin's tables, brachial muscle area (cm2) and total skeletal muscle mass (kg) calculated from Heymsfield's equations. On the third and fourth days, after 48 hours of meat-free and fish-free diet, 3-methylhistidine (mmol/g creatininuria) and creatinine (mg) were measured in urine, and the urinary creatinine/height ratio (mg/cm/day) was calculated. Full anthropomorphic measurements were performed on 19/32 patients and complete measurements of 3-methylhistidine and the urinary creatinine/height ratio in 9/32 patients. Subsequent examinations revealed a decrease in brachial muscle area, total skeletal muscle mass and urinary creatinine/height ratio which, together with an increase in baseline 3-methylhistidine, confirmed the loss of muscle mass. Mean losses of muscle and fat were 6 p. 100 between T1 and T0 and 7 p. 100 between T2 and T0 for the muscle mass, and 9 p. 100 between T2 and T0 for the fat mass. These losses of body mass occurred very early, with significant differences between T1 and T0 and between T2 and T0. They suggest that protein-calorie malnutrition develops at a very early stage in patients treated for cancer or malignant blood disease.

Fatty acid and glycerol kinetics in septic patients and in patients with gastrointestinal cancer. The response to glucose infusion and parenteral feeding

The rates of glycerol and free fatty acid (FFA) kinetics in normal volunteers (VOL), non-weight-losing (NWL) gastrointestinal cancer patients, weight-losing (WL) gastrointestinal cancer patients, and in severely septic patients, using constant infusions of d-glycerol and 1-13C palmitic acid; were determined. Rates of FFA oxidation have also been quantitated. Measurements were made in the basal state, during glucose infusion (4 mg/kg/min), and during total parenteral nutrition (TPN). Rates of glycerol and FFA appearance (Ra) in volunteers and NWL cancer patients were similar, and in both groups there was a significant suppression after glucose infusion. The basal Ra values for glycerol and FFA were 2.4 +/- 0.2 and 6.5 +/- 0.8 mumol/kg/min, respectively, in the volunteers, and in the NWL cancer patients the corresponding values were 2.7 +/- 0.4 and 7.1 +/- 1.1 mumol/kg/min (not significantly different). Compared with the volunteers, the rates of glycerol and FFA turnover were significantly elevated in both septic patients and WL cancer patients. The values for glycerol and FFA Ra were 6.3 +/- 1.1 and 13.1 +/- 3.0 mumol/kg/min, respectively, in the septic patients. The corresponding values were 4.1 +/- 0.4 and 11.7 +/- 1.6 mumol/kg/min in the WL cancer patients. In contrast to the response seen in the volunteers and NWL cancer patients, glucose infusion did not suppress lipolysis in either the septic or WL cancer patients. In all groups studied, glucose infusion resulted in an increase in FFA recycling. Despite the fact that the WL cancer patients had an increased FFA availability, they were significantly less able to oxidize either endogenous FFA or infused lipid when compared with NWL cancer patients (the basal % of FFA uptake oxidized in WL cancer patients was 10 +/- 2% vs. 18 +/- 3% in NWL cancer patients). In contrast, the septic patients had an enhanced capacity to oxidize either endogenous FFA or infused lipid (the basal % of FFA uptake oxidized was 40 +/- 8%, and during TPN this increased in 65 +/- 10%). From these studies the following was concluded: in terms of lipid kinetics, NWL cancer patients are not significantly different from volunteers; WL cancer patients and septic patients have elevated rates of lipolysis, and in contrast to what was seen in NWL cancer patients and in volunteers, glucose infusion in WL cancer patients and in septic patients does not result in a significant inhibition of lipolysis; and WL cancer patients have an impaired capacity to oxidize either endogenous FFA or infused lipid.(ABSTRACT TRUNCATED AT 400 WORDS)

Hydrazine sulfate in cancer patients with weight loss. A placebo-controlled clinical experience

Hydrazine sulfate was evaluated using 24-hour dietary recalls and body weight determinations before and after 30 days of either placebo or hydrazine (60 mg, 3 times/d) oral administration in 101 heavily pretreated cancer patients with weight loss. After 1 month, 83% of hydrazine and only 53% of placebo patients completing repeat evaluation maintained or increased their weight (P less than 0.05). In addition, appetite improvement was more frequent in the hydrazine group (63% versus 25%, P less than 0.05). Although caloric intake was only slightly greater in hydrazine-treated patients, an increased caloric intake was more commonly associated with weight gain in patients receiving hydrazine compared with those receiving placebo (81% versus 53%, respectively). Hydrazine toxicity was mild, with 71% of patients reporting no toxic effects. Hydrazine sulfate circulatory levels were obtained from a subset of 14 patients who completed 30 days of treatment, with a single sample obtained in the morning at least 9 hours after the last dose. Mean maintenance hydrazine sulfate levels, determined using a spectrofluorometric assay, ranged from 0 to 89 ng/ml (mean 45 +/- 16 ng/ml). These data, which demonstrate an association between 1 month of hydrazine sulfate administration and body weight maintenance in patients with cancer, suggest future clinical trials of hydrazine sulfate are indicated to definitively assess its long-term impact on important clinical outcome parameters in defined cancer populations.

Cancer cachexia

Cancer cachexia is a complex syndrome that includes host tissue wasting, anorexia, asthenia, and abnormal host intermediary metabolism. It is present in approximately 50% of cancer patients during treatment and nearly 100% of treated cancer patients at death. Cachexia has a detrimental impact on cancer therapy. The central problem of cancer cachexia is that energy balance is not maintained, and the host has a relative hypophagia which results in host tissue wasting. The tumor by its nature and obligate growth can continue to consume glucose, amino acids, and lipids at the expense of the host. This produces abnormal host intermediary metabolism including elevated glucose production and recycling, decreased muscle protein synthesis, and increased muscle and fat breakdown. The exact mechanisms of cancer cachexia have been only partially elucidated. The identification of signal molecules like cachectin which mediate these changes may be on the horizon. Nutritional support can reverse some of the derangements seen with cachexia, and there is evidence that functional lean body mass or body cell mass can be restored in some (but not all) patients. However, nutritional support has not yet improved response to chemotherapy or radiation therapy, nor has it improved host tolerance of chemotherapy. It has improved operative mortality and morbidity in cachectic cancer patients undergoing major surgical procedures. Optimum host nutritional support appears to be dependent on high insulin concentrations in both humans and rats. Insulin and exercise may be methods to preserve host lean tissue and feed the host rather than the tumor. Future studies depend on better definition of tumor-bearing host metabolism, altering the relationship between neoplasm and host to preferentially feed the host, and making the neoplasm more susceptible to effective treatment.

Nutritional support in the cancer-bearing host. Effects on host and tumor

Cancer patients have the highest prevalence of malnutrition of any group of hospitalized patients. The potential causes of this malnutrition are numerous, as elements of both starvation and stress are evident in the cancer-bearing host. The presence of the tumor alone may lead to reduced intake of nutrients and treatment modalities of surgery, chemotherapy, and radiation therapy further exacerbate nutritional deficits. It is clear that the tumor requires energy substrates to grow, and that these substrates are exacted from the host. Animal studies identify progressive nutritional depletion concomitant with increasing tumor growth during ingestion of a regular diet. This appears predominantly due to reduced dietary intake in addition to host metabolic alterations. In animal/tumor models deliberate dietary protein depletion results in severe host weight loss, but also causes diminished tumor growth rates. Dietary manipulation in these animal/tumor models have demonstrated methods of improving tumor response to chemotherapy by manipulation of tumor growth rates. In addition, drug-pharmacokinetics have been altered by dietary manipulation. However, data from animal/tumor models are not directly applicable to man since the tumor in animals usually results in the death of the host within six to eight weeks. Nevertheless, controlled laboratory studies in animals provide basic metabolic information which promotes understanding of host/tumor relationships in man. In cancer patients malnutrition has prognostic value, leads to a distortion of body composition with erosion of body protein and fat stores, and compromises the delivery of adequate therapy. There is no direct objective evidence of accelerated tumor growth in humans with cancer who receive nutritional support as part of their treatment regimen. The host benefits to the extent that body composition is at least maintained during the period of nutritional repletion. Thus, nutritional support provides support to the patient during periods of treatment and dietary deprivation. No improvement in the tumor's response to therapy, however, has been demonstrated by this approach.