Whole-body tyrosine flux in relation to energy expenditure in weight-losing cancer patients

Early-Onset Physical Inactivity and Metabolic Dysfunction in Tumor-bearing Mice Is Associated with Accelerated Cachexia

METHODS

Male C57BL/6J mice (12 wk of age) were injected with 1 × 106 LLC cells or phosphate-buffered saline (PBS) subcutaneously in the right flank, and tissue was collected 26-28 d after cell injection. Tumor volume was measured every 5 d throughout the study to calculate the tumor growth rate. Fifteen days after tumor inoculation, a subset of PBS (n = 11) and LLC (n = 16) mice were individually housed in metabolic Comprehensive Laboratory Animal Monitoring System cages for 5 d.

RESULTS

LLC mice exhibited greater body weight loss (-5.1%), decreased muscle mass (-7%), decreased fat mass (-22%), and increased plasma interleukin-6 (212%) compared with PBS mice. Before the onset of cachexia, total cage activity was decreased in tumor-bearing mice. Cage activity was negatively associated with tumor mass and positively associated with hindlimb muscle mass. In addition, LLC mice had greater lipid oxidation than PBS mice.

CONCLUSIONS

LLC mice exhibit early-onset physical inactivity and altered systemic lipid oxidation, which are associated with the eventual development of cachexia.

Validation Study of Energy Requirements in Critically Ill, Obese Cancer Patients

BACKGROUND

Current guidelines from the American Society for Parenteral and Enteral Nutrition and the Society of Critical Care Medicine (ASPEN/SCCM) regarding caloric requirements and the provision of nutrition support in critically ill, obese adults may not be suitable for similar patients with cancer. We sought to determine whether the current guidelines accurately estimate the energy requirements, as measured by indirect calorimetry (IC), of critically ill, obese cancer patients.

MATERIALS AND METHODS

This was a retrospective validation study of critically ill, obese cancer patients from March 1, 2007, to July 31, 2010. All patients ≥18 years of age with a body mass index (BMI) ≥30 kg/m(2) who underwent IC were included. We compared the measured energy expenditure (MEE) against the upper limit of the recommended guideline (25 kcal/kg of ideal body weight [IBW]) and MEE between medical and surgical patients in the intensive care unit.

RESULTS

Thirty-three patients were included in this study. Mean MEE (28.7 ± 5.2 kcal/kg IBW) was significantly higher than 25 kcal/kg IBW (P < .001), and 78% of patients had nutrition requirements greater than the current guideline recommendations. No significant differences in MEE between medical and surgical patients in the ICU were observed.

CONCLUSIONS

Critically ill, obese cancer patients require more calories than the current guidelines recommend, likely due to malignancy-associated metabolic variations. Our results demonstrate the need for IC studies to determine the energy requirements in these patients and for reassessment of the current recommendations.

Effect of tumor burden and subsequent surgical resection on skeletal muscle mass and protein turnover in colorectal cancer patients

BACKGROUND

Cachexia is a consequence of tumor burden caused by ill-defined catabolic alterations in muscle protein turnover.

OBJECTIVE

We aimed to explore the effect of tumor burden and resection on muscle protein turnover in patients with nonmetastatic colorectal cancer (CRC), which is a surgically curable tumor that induces cachexia.

DESIGN

We recruited the following 2 groups: patients with CRC [n = 13; mean ± SEM age: 66 ± 3 y; BMI (in kg/m(2)): 27.6 ± 1.1] and matched healthy controls (n = 8; age: 71 ± 2 y; BMI: 26.2 ± 1). Control subjects underwent a single study, whereas CRC patients were studied twice before and ~6 wk after surgical resection to assess muscle protein synthesis (MPS), muscle protein breakdown (MPB), and muscle mass by using dual-energy X-ray absorptiometry.

RESULTS

Leg muscle mass was lower in CRC patients than in control subjects (6290 ± 456 compared with 7839 ± 617 g; P < 0.05) and had an additional decline after surgery (5840 ± 456 g; P < 0.001). Although postabsorptive MPS was unaffected, catabolic changes with tumor burden included the complete blunting of postprandial MPS (0.038 ± 0.004%/h in the CRC group compared with 0.065 ± 0.006%/h in the control group; P < 0.01) and a trend toward increased MPB under postabsorptive conditions (P = 0.09). Although surgical resection exacerbated muscle atrophy (-7.2%), catabolic changes in protein metabolism had normalized 6 wk after surgery. The recovery in postprandial MPS after surgery was inversely related to the degree of muscle atrophy (r = 0.65, P < 0.01).

CONCLUSIONS

CRC patients display reduced postprandial MPS and a trend toward increased MPB, and tumor resection reverses these derangements. With no effective treatment of cancer cachexia, future therapies directed at preserving muscle mass should concentrate on alleviating proteolysis and enhancing anabolic responses to nutrition before surgery while augmenting muscle anabolism after resection.

Computational modeling of cancer cachexia

PURPOSE OF REVIEW

Measurements of whole-body energy expenditure, body composition, and in-vivo metabolic fluxes are required to quantitatively understand involuntary weight loss in cancer cachexia. Such studies are rare because cancer cachexia occurs near the end of life when invasive metabolic tests may be precluded. Thus, models of cancer-associated weight loss are an important tool for helping to understand this debilitating condition.

RECENT FINDINGS

A computational model of human macronutrient metabolism was recently developed that simulates the normal metabolic adaptations to semi-starvation and re-feeding. Here, this model was used to integrate data on the metabolic changes in patients with cancer cachexia. The resulting computer simulations show how the known metabolic disturbances synergize with reduced energy intake to result in a progressive loss of body weight, fat mass, and fat-free mass. The model was also used to simulate the effects of nutritional support and investigate inhibition of lipolysis versus proteolysis as potential therapeutic approaches for cancer cachexia.

SUMMARY

Computational modeling is a new tool that can integrate clinical data on the metabolic changes in cancer cachexia and provide a conceptual framework to help understand involuntary weight loss and predict the effects of potential therapies.

Activation of ATP-ubiquitin-dependent proteolysis in skeletal muscle in vivo and murine myoblasts in vitro by a proteolysis-inducing factor (PIF)

Loss of skeletal muscle is a major factor in the poor survival of patients with cancer cachexia. This study examines the mechanism of catabolism of skeletal muscle by a tumour product, proteolysis-inducing factor (PIF). Intravenous administration of PIF to normal mice produced a rapid decrease in body weight (1.55 +/- 0.12 g in 24 h) that was accompanied by increased mRNA levels for ubiquitin, the Mr 14 000 ubiquitin carrier-protein, E2, and the C9 proteasome subunit in gastrocnemius muscle. There was also increased protein levels of the 20S proteasome core and 19S regulatory subunit, detectable by immunoblotting, suggesting activation of the ATP-ubiquitin-dependent proteolytic pathway. An increased protein catabolism was also seen in C(2)C(12)myoblasts within 24 h of PIF addition with a bell-shaped dose-response curve and a maximal effect at 2-4 nM. The enhanced protein degradation was attenuated by anti-PIF antibody and by the proteasome inhibitors MG115 and lactacystin. Glycerol gradient analysis of proteasomes from PIF-treated cells showed an elevation in chymotrypsin-like activity, while Western analysis showed a dose-related increase in expression of MSSI, an ATPase that is a regulatory subunit of the proteasome, with a dose-response curve similar to that for protein degradation. These results confirm that PIF acts directly to stimulate the proteasome pathway in muscle cells and may play a pivotal role in protein catabolism in cancer cachexia.

Pathophysiology of cancer cachexia

Cancer cachexia is a frequent complication observed in patients with malignant tumors. Although several decades have passed since the first focus on the metabolic dysfunction's associated with cancer, few effective therapeutic interventions have been successfully introduced into the medical armamentarium. The present study thoroughly reviews the basic pathophysiology of cancer cachexia and the treatment options already investigated in that field. Experimental and clinical studies were evaluated individually in order to clarify the intricate alterations observed in tumor-bearing patients. The difficulties in introducing sound and effective nutritional support or metabolic manipulation to reverse cancer cachexia are outlined in this review.

Plasma amino acid concentrations in patients with acute myelogenous leukemia

Changes in plasma-free amino acid (PFAA) concentrations in the presence of solid tumors have been widely described. Conversely, the PFAA profile in patients with acute leukemias is less well defined. The aim of the present study was to clarify whether the PFAA profile is altered in patients with acute myeloid leukemia (AML), whether the profile differs from the PFAA profile of solid tumors, and whether it may predict outcome of AML. Fasting PFAA were measured in 40 untreated, normally nourished patients with AML (17 males, 23 females), ages 22-78 y, with white blood cell (WBC) counts ranging from 1.08 to 276.5 x 10(3)/cm2, and in 24 healthy volunteers. Plasma concentrations (mu mol/L, mean +/- SE) of glutamic acid (GLU), free tryptophan (FTRP), ornithine (ORN), and glycine (GLY) were significantly higher in AML (GLU: 90.2 +/- 6.1 versus 37 +/- 8; FTRP: 7.0 +/- 0.6 versus 4.8 +/- 0.3, P < 0.005; ORN: 108.7 +/- 5.8 versus 78 +/- 6, P < 0.001; GLY: 295.0 +/- 14.8 versus 239 +/- 9, P < 0.01), whereas serine (SER), methionine (MET), and taurine (TAU) were significantly lower in AML than in controls (SER: 109.0 +/- 5.8 versus 130 +/- 4, P < 0.03; MET: 25.5 +/- 1.3 versus 33 +/- 3, P < 0.03; TAU: 46.5 +/- 3.5 versus 81 +/- 2, P < 0.001), and tended to be even lower in patients who had not responded to chemotherapy or had relapsed within 18 mo of enrollment. Such changes were unrelated to age, sex, and WBC count. Changes in PFAA that occur in AML are only in part similar to those observed in solid tumors. The reduction of TAU appears to be a typical feature of AML and might be secondary to the deficiency of its precursors SER and MET. Further studies are under way aimed at clarifying whether PFAA might predict prognosis in AML, whether PFAA is normalized by remission induction, and if its correction may be of any benefit for patients with hematologic malignancies.

Metabolic alteration in patients with cancer: nutritional implications

During the past 20 years, efforts have been made to elucidate the metabolic changes observed in patients with cancer by using stable and radioactive isotopic tracers. These metabolic changes in patients with cancer may be similar to those in other stress conditions, in which glucose production and utilization, lipolysis and free fatty acid flux, and net protein catabolism are increased. Stress hormones, such as glucagon and catecholamines, and certain cytokines may be responsible for these metabolic changes. Although it has been shown that cachexia in patients with cancer signals a poor prognosis, efforts to improve the clinical outcomes with nutritional support have been disappointing. The failure of cancer patients to respond to nutritional support may be related to an alteration in the intermediate metabolism. Therefore, further research evaluating the metabolic abnormalities associated with cancer may lead to more effective nutritional therapies.

Metabolic response to radiation therapy in patients with cancer

The effect of radiation therapy on substrate metabolism was evaluated in five patients with head and neck or lung cancer. Stable isotope tracer methodology was used to determine urea, amino acid, glucose, and lipid kinetics during postabsorptive conditions before initiation, near the midpoint (after receiving 2,672 +/- 36 rads), and at completion (after receiving 6,072 +/- 307 rad) of a 6- to 8-week course of radiation therapy. Nutritional status was maintained throughout the treatment period by providing supplemental enteral feedings as needed. Postabsorptive plasma insulin, catecholamine, and amino acid concentrations did not change during the course of treatment. Before radiation therapy was initiated, values for the plasma rate of appearance (Ra) of urea (3.35 +/- 0.33 micromol x kg(-1) x min(-1)), alpha-ketoisocaproate ([alpha-KIC] 2.16 +/- 0.19 micromol x kg(-1) x min(-1)), phenylalanine (0.59 +/- 0.052 micromol x kg(-1) x min(-1)), and glucose (10.56 +/- 1.31 micromol x kg(-1) x min(-1)) were in the normal range. However, glycerol and palmitate Ra values (3.11 +/- 0.30 and 2.01 +/- 0.33 micromol x kg(-1) x min(-1), respectively) were 25% higher than values observed previously in normal subjects. Substrate flux did not change during radiation therapy, and measurements obtained during the midpoint and at completion of treatment were similar to initial values. These results demonstrate that large doses of radiation therapy, administered over 6 to 8 weeks to the upper body, do not cause significant metabolic stress.

Nutrition therapy for the cancer patient

Malnutrition commonly occurs in cancer and adversely affects the quality of life and survival of patients. It is caused by a variety of factors, including decreased food intake, adverse effects from anticancer treatment, and wasteful metabolic processes. Over the past 2 decades, there have been major advances in methods and techniques of feeding patients with cancer and other disease. Special diets can be helpful in the treatment of a variety of conditions, some of which are outlined in Table 1. Enteral feeding is developing rapidly because endoscopic techniques have made it simpler to place feeding tubes, and a variety of enteral feeding solutions are commercially available. Enteral feeding is an effective way to deliver nutrients when patients are unable to ingest food because of neurologic disorders or structural abnormalities in the upper gastrointestinal tract, including the oropharynx, esophagus, and stomach. The role of enteral feeding as an adjuvant to anticancer therapy has not been fully evaluated. Parenteral nutrition is an effective method of delivering nutrients into the blood stream. It has proved to be life-saving for patients with chronic severe gastrointestinal insufficiency (such as short bowel or radiation enteritis), whose cancer is cured or nonprogressive. Numerous studies have assessed the role of TPN as an adjuvant therapy. To date, a clear benefit from its routine use has been demonstrated only in very limited, specific situations. As an adjuvant to chemotherapy, TPN does not seem to be useful, unless there are prolonged periods of gastrointestinal toxicity (as in the case with bone marrow transplantation) that severely limit oral intake and absorption. Malnourished surgical patients undergoing specific major operations for cancer may benefit from perioperative TPN. TPN as an adjunct therapy in the treatment of the cancer patient has to be individually evaluated and appropriately applied in situations in which it has proven beneficial in randomized studies.

Altered metabolism and mortality in patients with colon cancer receiving chemotherapy

To identify the metabolic effects of 5-fluorouracil and hydrazine sulfate therapy, 22 patients with colon cancer were admitted prospectively to a Clinical Research Center for serial measurement of counter-regulatory hormones, fasting hepatic glucose production (HGP), intravenous glucose tolerance test, plasma leucine appearance (LA) and leucine oxidation. Combined therapy was associated with a significant reduction in fasting glucose level (98 +/- 2 mg/dL to 94 +/- 2, P < 0.025) without a significant fall in fasting HGP (2.09 +/- 0.11 mg/kg/min versus 2.03 +/- 0.13; P > 0.05). The decreased fasting glucose value was associated with a mild but not statistically improved glucose disposal rate in response to the intravenous glucose tolerance test (1.34 +/- 0.07 %/min vs 1.47 +/- 0.11, P = 0.15). Plasma leucine appearance was significantly reduced after 2 months of therapy (63.3 +/- 3.0 mumol/kg/hr vs 57.1 +/- 3.9 mumol/kg/hr; P < 0.025), but leucine oxidation (11.5 +/- 1.1 mumol/kg/hr vs 11.2 +/- 1.1 mumol/kg/hr) was not altered. Despite the fact that plasma triiodothyronine concentrations significantly increased with therapy, it was not associated with plasma LA. Half of the patients with cancer died 14 +/- 4 months after the study, and the other half were alive 58 +/- 2 months later. Survival time can be estimated with 59% accuracy using plasma LA, HGP, carcino-embryonic antigen, and insulin concentration. Multiple regression analysis identified that plasma LA was related directly to length of survival time, and baseline HGP, carcino-embryonic antigen, and insulin concentration were related inversely to length of survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Energy expenditure in patients with hepatocellular carcinoma

BACKGROUND

An increase in resting energy expenditure (REE) is considered to contribute to the weight loss experienced by patients with cancer. However, alternations in basal metabolism vary among patients with different neoplasms. REE in patients with hepatocellular carcinoma (HCC), a common malignant tumor in Taiwan, was evaluated.

METHODS

Fifty-seven male patients with HCC and 60 male control subjects without known cancer were entered in the study. The groups did not differ significantly in age, body weight, and height. Indirect calorimetry was used to measure REE. Oxidative rates of endogenous substrates also were calculated.

RESULTS

REE was significantly higher in the HCC group than the control group (22.12 +/- 0.36 kcal/kg/day versus 20.99 +/- 0.27 kcal/kg/day, P < 0.05; and 115.3 +/- 4.3 kcal/100 mg creatinine versus 102.2 +/- 3.8 kcal/100 mg creatinine, P < 0.05). A higher measured-to-predicted-REE ratio also was observed in the HCC group (101.5% +/- 1.4% versus 93.6% +/- 1.0%; P < 0.005). REE in patients with HCC did not differ according to whether patients had liver cirrhosis or ascites. In addition, REE of patients with large and medium tumors were higher than were those of patients with small tumors, but no difference was found between the REE of patients with small tumors and the control subjects. Also observed were an increase in oxidation of fat with a decrease in oxidation of protein in patients with HCC and a relative decrease in the contribution of fat with an increase in the contribution of carbohydrates to REE after the increase of tumor size.

CONCLUSIONS

The results suggest that patients with HCC are hypermetabolic and the elevation in REE is related to tumor size, not to the presence of liver cirrhosis or ascites.

Pathophysiology of cancer cachexia

Patients with advanced cancer and cachexia typically demonstrate modestly increased rates of energy expenditure in the presence of diminished food intake due to anorexia and to gastrointestinal disturbances. Rates of glucose production by the liver, gluconeogenesis and glycolysis to lactate (Cori cycle) are increased, fat mobilisation and oxidation are accelerated. There is a redistribution of body proteins away from muscle towards visceral proteins, resulting in marked muscle protein loss. Cancer cachexia differs from simple starvation and demonstrates metabolic similarities to sepsis or polytrauma. The metabolic response in the patient with cancer is largely due to mediators released by the tumour or by the host; recently the role of cytokines such as tumour necrosis factor alpha (TNF alpha), interleukin-1 (IL-1) and -6 (IL-6) and interferon gamma (INF gamma) has been emphasized. Catabolic hormones such as glucocorticoids and adrenaline have also been implicated. Cytokines have the potential to reproduce experimentally the clinical syndrome of cancer cachexia. There is evidence of increased production of several of them in certain types of cancer. There are overlapping activities of the cytokines TNF alpha, IL-1, IFN gamma and IL-6. The contribution of each of them to cancer cachexia remains unclear. Inhibition of cytokine activity using specific antibodies in cancer-bearing experimental animals demonstrated partial prevention of cachexia. A positive feedback between macrophage-derived IL-1 and tumour-derived IL-6 has been demonstrated recently in experimental cancer cachexia. Cytokines may support tumour growth by acting as growth factors.

Protein turnover in advanced lung cancer patients

Understanding the extent to which changes in whole-body protein kinetics contribute to the commonly observed weight loss and decrease in lean body mass (LBM) in patients with cancer is currently obscured by conflicting reports in the literature. While several studies have reported significant increases in whole-body protein turnover (WBPT), synthesis (WBPS), and catabolism (WBPC) in patients with cancer, others have failed to confirm these observations. We have measured whole-body protein kinetics using a primed constant infusion of 15N-glycine in a homogenous group of 32 newly diagnosed advanced lung cancer patients with comparable staging and before any antineoplastic treatment, and in 19 normal healthy volunteer controls. Urinary urea and ammonia 15N enrichment was determined in individually collected urine samples obtained during the 24-hour study period and averaged for the determination of protein kinetics. During the last 6 hours of urine collection, samples were obtained hourly for determination of 15N plateau enrichment. Twenty-four-hour urinary nitrogen and creatinine excretion was determined from 24-hour pooled urine samples. Resting metabolic expenditure (RME) was determined by indirect calorimetry and LBM was estimated from deuterium oxide dilution. Age body weight, LBM, RME, and 24-hour urinary nitrogen excretion did not differ between cancer and control subjects. WBPT, WBPC, and WBPS (g/kg/d) were significantly increased in lung cancer patients. However, when the same results were expressed either per kilogram LBM or per gram 24-hour urinary creatinine excretion, WBPT, WBPC, and WBPS rates were not statistically different from those of the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein and amino acid metabolism in cancer cachexia: investigative techniques and therapeutic interventions

Cancer cachexia is a complex syndrome characterized primarily by diminished nutrient intake and progressive tissue depletion that is manifest clinically as anorexia and host weight loss. The gradual loss of host protein stores is central to this process. This review outlines the techniques that have been used to evaluate human amino acid metabolism, their application in patients with cancer cachexia, and possible therapeutic interventions designed to overcome alterations in host protein and amino acid metabolism associated with malignant cachexia. The techniques of nitrogen balance and 3-methylhistidine excretion provide indirect estimates of overall nitrogen metabolism and skeletal muscle myofibrillar protein breakdown. Measurement of circulating amino acid concentrations, particularly when combined with assessment of arterial-venous differences and regional amino acid balance allows for investigation of interorgan amino acid metabolism. One of the most significant advances in in vivo amino acid metabolic research has been the development of labeled amino acid tracer studies to evaluate whole body and regional amino acid kinetics. The use of stable and unstable amino acid isotopes in these techniques is reviewed in detail. Virtually all of these techniques have now been employed in the evaluation of human cancer cachexia. The results of studies evaluating amino acid concentrations, regional amino acid balance, and 3-methylhistidine excretion are summarized. The use of regional and whole body kinetic studies in cancer cachexia are reviewed extensively. Most investigators have observed increased rates of whole body protein turnover, synthesis, and catabolism in both weight-stable and weight-losing cancer patients. Some studies have suggested a relationship between the extent of disease and the degree of aberration in amino acid kinetic parameters. Investigators have attempted to reverse some of these alterations by provision of substrate (nutritional support) or administration of specific pharmacologic or anabolic agents such as hydrazine sulfate, insulin, growth hormone, and beta-2 agonists. The role of total parenteral nutrition (TPN) in cancer and its effects on protein and amino acid kinetics and tumor growth are addressed. The possible benefits of specific amino acid nutritional formulations with increased branched chain amino acids, arginine, and glutamine are reviewed. Although many of these approaches appear promising, significant impact on clinically definable parameters remains to be demonstrated. A better understanding of the underlying protein catabolic mechanisms of cancer cachexia will likely lead to more effective therapies to reverse the protein calorie malnutrition associated with cancer cachexia.

Metabolic response to chemotherapy in colon cancer patients

The goal of this investigation was to identify the metabolic abnormalities in a group of colon cancer patients before and during 5-fluorouracil chemotherapy. Twenty-two colon cancer patients were prospectively enrolled into a Clinical Research Center for measurement of counter regulatory hormones, fasting hepatic glucose production (HGP), intravenous glucose tolerance test, plasma leucine appearance (LA), and leucine oxidation (LO). Both the cancer group and the normal volunteers were matched for nutrition status (109 +/- 5% of ideal body weight vs 104 +/- 4%, mean +/- SEM, respectively) and history of weight loss (6.3 +/- 2.6 kg vs 4.4 +/- 4.8). Plasma growth hormone was significantly elevated in the colon cancer patients (3.22 +/- 0.62 ng/mL vs 0.73 +/- 0.18, p < .05) despite the fact that insulin-like growth factor-1 levels were not different. Plasma glucose, insulin, cortisol, glucagon, epinephrine, and norepinephrine levels were not significantly different than those of the normal volunteers. Fasting HGP rates were slightly but not significantly elevated in the group of colon cancer patients compared with the normal volunteers (2.09 +/- 0.11 mg/kg per minute vs 1.79 +/- 0.10, p = .10). Plasma LA was not significantly elevated in the colon cancer group (63.3 +/- 3.0 mumol/kg per hour vs 57.7 +/- 4.2; p = .25). Five days of continuous 5-fluorouracil chemotherapy was associated with a significant elevation in both the fasting glucose level (97 +/- 3 mg/dL vs 106 +/- 5, p < .05), and HGP (2.09 +/- 0.11 mg/kg per minute vs 2.27 +/- 0.10; p < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Amino acid profiles correlate diagnostically with organ site in three kinds of malignant tumors

The hypothesis that tumors arising in a particular organ site impose a characteristic plasma free amino acid (PFAA) pattern was tested by analyzing PFAA in fasting venous blood of preoperative patients with breast cancer, gastrointestinal tract cancer, and head and neck cancer. Healthy volunteers served as control subjects. Levels of 28 PFAA were determined in blood samples using an amino acid analyzer, and the data were compared using discriminant analysis and chi-square testing. Compared with control subjects, the concentrations of seven amino acids (glutamine, threonine, histidine, cysteine, alanine, arginine, and ornithine) in patients with tumors correlated closely with the known diagnoses. By means of discriminant analysis, these seven amino acids had the highest correlation with the specific diagnoses, indicating that PFAA profiles correlate diagnostically with the organ-site origin of three different kinds of malignant tumors.

Insufficient effect of total parenteral nutrition to improve protein balance in peripheral tissues of surgical patients

Previous studies have indicated that unstressed and malnourished patients do not necessarily obtain amino acid balance across peripheral tissues during total parenteral nutrition (TPN) treatment, indicating treatment inefficiency. Therefore, the aim of this study was to evaluate to what extent (prevalence) insufficient therapeutic amino acid balance occurs in surgical patients receiving TPN for standard medical reasons. Thirty-two patients treated in an ordinary surgical ward (n = 17) or in the intensive care unit (ICU) (n = 15) were examined. The arteriovenous balance across the leg of amino acids, glucose, glycerol, lactate, and oxygen was measured in relationship to plasma levels of insulin. All patients had been receiving TPN for at least 7 days before the investigation. All measurements were performed when amino acids had been infused for at least 4 hours and thus expected to support the resynthesis of lean body mass. Patients treated in the ICU and the surgical ward were in positive whole-body energy balance (+1127 +/- 121 and +917 +/- 123 kcal, respectively). Glucose uptake and oxygen consumption across the leg were similar in both patient groups. Glycerol release was not different from zero balance, indicating that inhibition of lipolysis across the leg during feeding and lactate was normally released in both groups. However, approximately 50% of the patients treated in the ordinary ward and 80% to 100% of the patients in the ICU remained in negative amino acid balance across the leg as judged from significant release of either methionine, tyrosine, or phenylalanine despite concomitant infusion of amino acids (approximately 0.3 g of N per kilogram per day) and nonprotein calories.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin time-dependent effects on the leg exchange of glucose and amino acids in man

Time-dependent effects of insulin on the leg exchange of glucose, lactate, glycerol, free fatty acids (FFA) and amino acids were measured in relation to oxygen uptake (leg and whole body) and whole body glucose assimilation including oxidation. Seven healthy males (58 +/- 3 years of age) were investigated before operation of uncomplicated inguinal hernia or varicose veins. Euglycaemic glucose clamp investigations with systemic hyperinsulinaemia between 100-120 mU1(-1) were used. Metabolic measurements were performed before and during hyperinsulinaemia at 2 and 6 h following the start of glucose clamp to evaluate the time-dependency of insulin actions. Whole body glucose uptake increased continuously for up to 6 h (from 4.7 +/- 0.7 to 8.0 +/- 0.8 mg/kg/min, P less than 0.01) despite stable plasma concentrations of glucose and insulin. This was also true for glucose oxidation. Whole body oxygen uptake did not change significantly during the clamp while the leg exchange of oxygen uptake did (from 5.9 +/- 0.86 mumol/100 g/min to 11.6 +/- 2.4, P less than 0.01). Insulin effect on leg blood flow was time-dependent and increased two-fold (2.3 +/- 0.4 ml/100 g/min to 4.4 +/- 0.9, P less than 0.001) during clamp. The leg production of lactate increased continuously, accounting for approximately 15% of the glucose uptake across the leg, but the rise in arterial lactate did not reach the level of statistical significance. Plasma FFA concentrations decreased in a time-dependent manner during clamp, while the leg exchange of FFA switched rapidly to a stable net uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Energy expenditure and protein synthesis rates in an animal model of cancer cachexia

Food intake and energy expenditure of cachectic tumour bearing mice were measured during the course of weight loss. Four weeks after implantation of the MAC-16 tumour the body weight was reduced by 20%, there was no significant reduction in food intake, and body composition analysis revealed that both body fat and protein mass were decreased. Oxygen consumption and carbon dioxide production were measured over a 24h period both before and at weekly intervals after tumour implantation. There was a gradual increase in the rates of both oxygen consumption and carbon dioxide production per gram body weight. Similarly, energy expenditure per gram body weight was increased during the 3rd (11%) and 4th (23%) weeks. In contrast, the food intake per gram body weight was unchanged during the first three weeks and increased by only 8% during the 4th week. Despite the development of cachexia, rates of protein synthesis in the liver, heart, kidney and skeletal muscle were the same four weeks after tumour implantation as those in non-tumour bearing mice. Thus, in this murine model of cancer cachexia a negative energy balance resulted from failure of food intake to compensate for increased energy demands. These findings point to the unique pattern of metabolic alterations which occur in different models of cancer cachexia.

Elevated energy expenditure in cancer patients with solid tumours

Cancer patients (n = 106) and non-cancer subjects (n = 96) were classified as weight stable (n = 70) or weight-losing (n = 132). Cancer patients had elevated resting energy expenditure (REE) compared with either weight-losing (23.6 [0.4] vs. 20.5 [0.5] kcal/kg per day, P less than 0.001) or weight-stable controls (22.0 [0.6] vs. 17.9 [0.4], P less than 0.001). Cancer patients had increased fat oxidation irrespective of weight loss (1.24 [0.07] vs. 0.87 [0.04] mg/kg per min; 1.07 [0.04] vs. 0.78 [0.04], P less than 0.001). Elevated energy expenditure was counter-regulated by a decrease in thyroid hormones. Abnormal liver function had no impact on REE in either group. Heart rate was the most powerful factor for prediction of high energy expenditure in both patients and controls. Elevated energy expenditure was related to the increased heart rate in cancer patients in a significantly higher proportion than that in controls. Increased metabolic rate is a significant component behind weight loss in cancer disease, independent of malnutrition and an elevated adrenergic state may be a likely explanation.

Elevated circulating interleukin-6 is associated with an acute-phase response but reduced fixed hepatic protein synthesis in patients with cancer

It has been suggested that, as part of the inflammatory response to the presence of a tumor, various cytokines are produced and these induce hepatic synthesis of acute-phase proteins (APP). Under these circumstances it is not known what changes occur in the fixed component of hepatic protein synthesis. The aim of this study was to compare circulating interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF) concentrations and fixed hepatic protein synthesis rates in a group of healthy controls (n = 6) with a group of patients with an established APP response secondary to hepatic metastasis from colorectal cancer (n = 6). Fixed hepatic protein synthesis rates were measured following a primed, constant 20-hour infusion of 15N-glycine. The liver was biopsied at laparotomy. The APP response was assessed by serum C-reactive protein concentration and cytokines were assayed by a combination of immunoassay and bioassay. The patients with advanced cancer and an on-going APP response had elevated circulating IL-6 concentrations (p less than 0.01). Rates of fixed hepatic protein synthesis were 30% lower than those observed in controls (p less than 0.01). These findings demonstrate that in patients with hepatic metastasis, although the synthesis of certain acute-phase export proteins can be increased, fixed protein synthesis is reduced. Whether these changes in the distribution of hepatic protein synthesis are mediated by IL-6 will require further investigation.

Effect on whole-body protein synthesis after institution of intravenous nutrition in cancer and non-cancer patients who lose weight

Cancer and non-cancer patients received total parenteral nutrition (TPN) corresponding to either 120% or 200% non-protein energy resting energy expenditure. Whole-body tyrosine flux and leg exchange of various metabolites were measured in the fasted and fed state. Feeding with the moderate TPN rate did not stimulate whole-body protein synthesis in either group, but the high rate did. Both TPN rates switched an efflux of branched-chain aminoacids from the leg to an uptake in both groups, but this did not apply to tyrosine or phenylalanine. Only the high TPN rate stimulated glucose uptake across the leg in both groups. The leg exchanges of lactate, glycerol and free fatty acids were not significantly influenced by moderate or high TPN rates in either group, although changes in arterial concentrations indicated significant exchanges in compartments other than leg tissues. Thus standard TPN is insufficient to stimulate overall protein synthesis in both malnourished cancer and non-cancer patients, which may explain why previous studies have demonstrated insignificant functional effects with nutritional support to cancer patients.

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.

The aetiology and management of weight loss and malnutrition in cancer patients

Abnormal values of parameters generally associated with description of protein or energy stores are often observed in cancer patients. The aetiology of these abnormal values is not clear, but seems to include insufficient energy intake absolutely (anorexia), or relative to energy needs (increased energy expenditure). In addition, the ability of some tissues to acquire nitrogen and energy seems to be changed when cancer is present. The resulting status described by abnormal values of protein or energy store parameters is often incorrectly referred to as malnutrition. Incorrect because many factors other than nutrition are related to the development of this condition. However, the presence of the so-called malnutrition is associated with increased morbidity, decreased survival and decreased tolerance to cancer therapy. Whether nutritional therapy is able to reverse these adverse effects by malnutrition remains unproven: most trials performed in an attempt to prove such restoration of the individual's ability to withstand cancer and its treatment, display such conceptual flaws that a convincing answer cannot be given. On the other hand, a deleterious effect of nutritional support has not been observed. More, and clinically relevant, research needs to be performed in this field.

The inefficiency of total parenteral nutrition to stimulate protein synthesis in moderately malnourished patients

The acute whole-body and peripheral tissue protein response to total parenteral nutrition (TPN) was evaluated before surgery in moderately malnourished patients with stable disease. A primed constant infusion of (U-14C) tyrosine was used in combination with simultaneous measurements of the leg exchange of amino acids, glucose, glycerol, and free fatty acids (FFA). Energy expenditure was measured by indirect calorimetry. Sixteen patients with stable disease and in need of nutritional support were randomized to receive TPN at rates either corresponding to resting requirements (nonprotein calories at 120% of REE with 0.2 g of N/kg/d) or at increased rates (200% of REE with 0.33 g of N/kg/d). Energy expenditure was not affected by the low rate of TPN, but increased with the high rate, with a thermic effect corresponding to 16% of basal levels. Tyrosine flux and incorporation rate into whole-body proteins (protein synthesis) were not altered by the low TPN rate, but increased with the high rate. Estimates of protein breakdown decreased, and tyrosine oxidation increased significantly with both rates of TPN. Protein synthesis was stimulated at the high dose rate only. However, a positive whole-body tyrosine balance (net protein synthesis) measured by the 14C tyrosine technique was associated with a continued negative tyrosine balance across the skeletal muscle compartment in the leg. The results demonstrate that TPN given at rates corresponding to resting needs of 0.2 g of N/kg/day is insufficient to promote protein synthesis in the majority of body proteins. Skeletal muscles may remain in negative protein balance even at high TPN loads. Our results reflect the difficulties of expanding lean body mass through intravenous nutrition in moderately malnourished patients--even those with stable disease.

Whole body fat oxidation before and after carnitine supplementation in uremic patients on chronic haemodialysis

This study has evaluated whether uremic patients on chronic haemodialysis with subnormal plasma levels of free carnitine show any alterations in whole body fat oxidation before and after one week with carnitine supplementation (60 mg/kg/day). Carnitine plasma levels changed from subnormal to supranormal levels of both free and total carnitine concentrations. This increase was not associated with any alteration in either oxygen uptake, carbon dioxide production, respiratory quotient or blood substrate levels such as glucose, glycerol, free fatty acids and lactate. The fractional oxidation of an intravenously infused fat emulsion (Intralipid) was 17% before and 19% after carnitine supplementation. No side effects were observed in spite of the rather high dose of carnitine administration. This study failed to demonstrate any impact on net whole body fat oxidation in carnitine substituted uremic patients with initially subnormal levels of free plasma carnitine.

Cancer cachexia

Despite recent advances in the delivery of nutritional support, cachexia continues to contribute to the morbidity and mortality of cancer patients. This impasse has called for a review of the many factors that are believed to be associated with weight loss in the cancer host. This article reviews the topic with a view to past problems and areas for investigation in the future.

Energy requirements for cancer patients and the effect of total parenteral nutrition

Limited data are available concerning resting metabolic expenditure (RME) in cancer patients and the effect of RME by varying glucose intake. This study describes the measurements on 21 patients with colorectal cancer while fasting and with incremental levels of standard TPN-glucose system by central vein. Following an overnight fast, the measured mean +/- SEM percent difference from the predicted RME for the male group was 4.13 +/- 1.67% and the female group, 2.09 +/- 2.09%. The overall mean percent difference of 2.95 +/- 1.45 suggests that colorectal cancer does not cause an increase in energy expenditure. Hepatic metastases in 11 of the patients did not influence RME. The data from the 21 patients indicate a statistically significant increase in RME with TPN compared to postabsorptive states in females of 37%, in males 21.88%, and combined of 29.88%. Progressively greater increases in RME were seen when calories provided incrementally exceeded the basal RME. Carbohydrate loading in excess of the patient's calorie need, as indicated by the respiratory quotient (RQ) greater than 1.0, results in fat synthesis and other energy-costing processes. The basal RME demonstrates that these cancer patients are not hypercatabolic, but do respond to high-level force-feeding with markedly increased metabolic expenditures.

Transport kinetics of amino acids across the resting human leg

Flux rates of amino acids were measured across the leg after an overnight fast in resting human volunteers. A balanced amino acid solution was, after a primed infusion, continuously infused for 2 h at each of three step-wise and increasing rates corresponding to 8.3, 16.7, 33.2 mg N/kg per h that were equivalent to 0.2, 0.4, 0.8 g N/kg per d. Flux of amino acids across the leg was compared with the flux of glucose, glycerol, lactate, free fatty acids, and oxygen. The size of the muscular tissue pool of amino acids was measured. Whole body amino acid oxidation was estimated by means of the continuous infusion of a 14C-labeled mixture of amino acids. Arterial steady state levels were obtained for most amino acids within 30 to 45 min after the primed constant infusion. Leg flux of amino acids switched from a net efflux after an overnight fast to a balanced flux between infusion rates corresponding to 0.2-0.4 g N/kg per d. At 0.8 g N/kg per d essentially all amino acids showed uptake. The infusion of amino acids stimulated leg uptake of glucose and lactate production and decreased FFA release. Oxygen uptake and leg blood flow increased significantly with increased infusion of amino acids. There was significant variability in transport rate among individual amino acids. Branched chain amino acids showed rapid transport and methionine slow transport rate. Only small changes in the muscle tissue concentration of certain amino acids were registered after 6 h of amino acid infusion despite uptake for several hours. When amino acids were infused at a rate corresponding to 0.8 g N/kg per d, the leg uptake of amino acids was 6% and the simultaneous whole body oxidation of infused amino acids was approximately 10%. Net uptake of leucine across the leg per hour was 62% of the muscle pool of free leucine when amino acids were infused at a rate corresponding to 0.4 g N/kg per d. Multiple regression analysis showed that the arterial concentration of an amino acid was the most important factor for uptake, more so than insulin concentration and blood flow. It is concluded that leg exchange of amino acids is large enough to rapidly change the pool size of the amino acids in skeletal muscle, if not counter-regulated by changes in rates of protein synthesis and degradation. Estimates of the capacity for protein synthesis and transfer RNA acceptor sites in muscles agree in order of magnitude with the net uptake of amino acids at high infusion rates of amino acids. Therefore, measurements of the balance of tyrosine, phenylalanine, and particularly methionine at steady state may reflect net balance of proteins across skeletal muscles even in short-time experiments.

Optimal nutritional indexes in cancer patients

This paper reviews various parameters that are used to assess the nutritional and functional status of cancer patients. Available information shows that the nutritional status of cancer patients is correlated with their overall prognosis and outcome. However, little information exists concerning the use of nutritional indexes to evaluate the effectiveness of nutritional rehabilitation of cancer patients. It is emphasized that we should concentrate on developing nutritional parameters to assess the functional improvement of patients rather than their body structure and composition.

Effect of hydrazine sulphate on whole-body protein breakdown measured by 14C-lysine metabolism in lung cancer patients

In a prospective double-blind trial twelve malnourished patients with lung cancer were randomised to receive either placebo or hydrazine sulphate (60 mg three times daily) for 30 days. Fasting lysine flux was determined by a primed 4-hour continuous infusion of 14C-lysine before and after one month of hydrazine treatment. Baseline plasma lysine flux was 2580 (SD 580) mumol/h for the placebo group and 2510 (440) mumol/h for the hydrazine group. After one month the placebo group showed a slight rise to 2920 (450) mumol/h (p = 0.08) and the hydrazine group showed a significant fall to 1840 (750) mumol/h (p less than 0.05); serum albumin fell in the placebo group and was unchanged in the hydrazine group. Administration of hydrazine sulphate to reduce aminoacid flux may favourably influence the metabolic abnormalities in cancer cachexia.

Thermic effect and substrate oxidation in response to intravenous nutrition in cancer patients who lose weight

This study examined oxidative metabolism and thermogenesis in the acute response to controlled intravenous nutrition in seven cancer patients who lost weight. Six weight-losing and malnourished patients without cancer served as controls. Indirect calorimetry was used and measurements of arterial concentrations of various substrates, metabolic end products, and insulin were performed. Resting energy expenditure (REE) was measured after an overnight fast. The resting energy need was calculated for each patient according to REE. The nutrition program consisted of glucose and lipids (Intralipid KabiVitrum AB, Stockholm, Sweden) each as 50% of nonprotein calories and amino acids (6.9 mg N/kcal). These substrates were infused simultaneously at rates equivalent to one, two, and three times REE, over periods of 6.5 hours on 3 consecutive days after a 12-hour fast. Arterial substrate levels and energy expenditure were measured between 6 and 6.5 hours after the start of the infusion. The cancer patients had well-recognized metabolic changes in the fasted state, such as elevated plasma levels of glycerol, triglycerides, free fatty acids, and lactate, and higher energy expenditure than predicted. The cancer patients responded to strictly defined substrate challenge in a similar way as the malnourished patients without cancer. Whole body oxidative capacity and the proportion of infused glucose and lipids that were oxidized at different levels of infusion rates were not decreased in cancer patients compared with control patients. Similar arterial substrate concentrations among the groups during infusions argues for a maintained plasma clearance of the substrate in the cancer patients. This study supports the suggestion that cachectic cancer patients can generate and conserve energy normally in response to intravenous nutrition. This refers to cancer patients with a history of weight loss up to 15% of their normal body weight. Therefore, weight loss due to altered tumor-host metabolism in cancer patients is of quantitative importance in the fasted state rather than in the fed state.

Some practical and theoretic concepts in the nutritional assessment of the cancer patient

Two patterns of response, that due to starvation or semistarvation and that due the stress, determine whether protein-calorie malnutrition of the adult marasmus variety or hypoalbuminemic malnutrition will occur in any particular nonmalignant disease. The latter condition can have two major components, the neuroendocrine response to injury, which is in large measure mediated by hormones of the hypothalamus and adrenal gland, and the panoply of responses to interleukin-1 production and release by macrophages and monocytes upon activation, usually by phagocytosis. In some cancer patients with weight loss there are many similarities to an interleukin-1 response including increases in resting energy expenditure, whole-body protein flux and synthesis and glucose flux and recycling, hypoalbuminemia and increased albumin catabolic rates, and an adaptive low T3 state that suggest a similar injury/infection response. Separation of cancer patients with malnutrition into those with an injury/infection response and those with simple starvation may explain the heterogeneous response to nutritional support among malnourished cancer patients and suggest new feeding regimens that may uniquely benefit the stress form of cancer malnutrition.

General metabolic abnormalities in cancer patients: anorexia and cachexia

Cancer cachexia is a chronic wasting illness directly associated with the presence of uncontrolled malignancy. The authors discuss the various causes of inadequate nutrient intake, including the known data on anorexia, and outline the potential role of humoral factors as mediators of cachexia.

Cancer and protein metabolism

We have reviewed the data that indicate that protein depletion is an important problem in cancer patients. An incomplete, yet useful, idea of the underlying mechanisms emerges. Further, we have seen that the provision of nutritional support may have a beneficial effect on patients with cancer, and we have explored areas of recent advances in nutritional formulation as regards energy and nitrogen source. Finally, data regarding micronutrients affecting nitrogen metabolism were reviewed. The extent to which tumor metabolism and changes secondary to the tumor-bearing state are influenced by micronutrients is not known. Traditional regimens based on the requirements of normal subjects or noncancer patients may not be relevant to the metabolic needs of the cancer patient. This could explain in part the failure of nutritional intervention trials to demonstrate a consistent benefit of nutritional support to the cancer patient. Further information regarding micronutrient needs in normal humans and cancer-bearing patients and their utilization by malignant tumors will have to be obtained.

Thermogenic effect of food in physically well-trained elderly men

Basal metabolic rate (BMR) and the thermogenic effect of food (TEF) after a liquid mixed meal of 2092 kJ (500 kcal) were examined in physically well-trained, elderly men in comparison with sedentary weight- and age-matched controls. BMR tended to be higher and TEF was significantly higher in the physically well-trained men than in the controls. No certain differences were found in plasma thyroid hormones or catecholamines. BMR correlated with whole body potassium while TEF did not. The tendency to elevated BMR in the well-trained men might therefore be due to their greater muscle mass. The elevated TEF, however, probably has other causes and might be associated with the elevated catecholamine sensitivity associated with the physically trained condition.

Improved protein kinetics and albumin synthesis by branched chain amino acid-enriched total parenteral nutrition in cancer cachexia. A prospective randomized crossover trial

A prospective randomized crossover trial was conducted to determine the effect of a branched chain amino acid (BCAA)-enriched solution on whole body leucine kinetics and fractional rates of albumin synthesis in patients with intra-abdominal metastatic adenocarcinoma. Ten malnourished cancer patients were provided isonitrogenous amounts of both a conventional total parenteral nutrition (TPN) formula containing 19% BCAA and a BCAA-enriched TPN formula containing 50% of the amino acids as BCAA in a random order. Whole body protein turnover was determined by a 10 hour continuous infusion of leucine 14C. Increased whole body leucine flux (68 +/- 5 mumols/kg BW/hr versus 145 +/- 11; mean +/- SEM; P less than 0.001) and oxidation (13 +/- 2 mumols/kg BW/hr to 46 +/- 5; P less than 0.001) were determined on the BCAA-enriched TPN. Increased whole body protein synthesis (2.2 +/- 0.2 g protein/kg BW/day versus 3.9 +/- 0.3; P less than 0.005) and leucine balance (2.5 +/- 0.4 g leucine/d versus 6.5 +/- 0.6; P less than 0.001) were also observed in patients receiving the BCAA-enriched TPN solution. Leucine release from protein breakdown was not statistically elevated (1.65 +/- 0.18 g protein/kg BW/d versus 2.48 +/- 0.40; P greater than 0.05) but, incorporation of leucine 14C into plasma albumin was significantly elevated (2.37 +/- 0.23 mumols/g/hr to 4.21 +/- 0.33; P less than 0.001) when the patients received BCAA-enriched TPN. Despite the better leucine balance, the improvement in the 24-hour urinary nitrogen balance was not statistically significant (6.6 +/- 3.9 g protein/d versus 11.4 +/- 2.9; control versus BCAA-enriched; P = 0.15). BCAA-enriched formulas improve whole body leucine kinetics, fractional rates of albumin synthesis, and leucine balance, and thus may favorably influence protein metabolism in cancer cachexia.

Metabolic and morphologic changes in brown adipose tissue from non-growing mice with an isogeneic sarcoma. Evaluation with respect to development of cachexia

Brown adipose tissue plays a thermoregulatory role influencing energy balance in experimental animals and possibly also in humans. In the present study we have reevaluated whether brown adipose tissue may contribute to the development of cancer cachexia in non-growing mice bearing an isogeneic tumor. Interscapular brown adipose tissue mass decreased by 20% in freely-fed sarcoma-bearing mice housed at room temperature. Increased mitochondrial density and increased oxidation rate of acetate at low acetate concentrations were found in brown fat from sarcoma-bearing mice, while the oxidation capacity was unchanged compared with that of freely-fed controls. Metabolic and morphologic changes in brown fat from sarcoma-bearing mice were similar to those found in weight-paired controls, which had experienced the same loss of body weight as the tumor-bearing mice. Selective and non-selective B-receptor blockade and surgical removal of interscapular brown fat before tumor implantation did not influence the nutritional state of freely-fed tumor-bearing mice. Injections of noradrenaline caused a proportionately lower increase in oxygen uptake in tumor-bearing animals than in freely-fed controls. Exposure to cold (+5 degrees C) doubled food intake and led to hypertrophy of brown fat in both sarcoma-bearing mice and control animals. Tumor growth was lower although not statistically different in animals housed at +5 degrees C compared with animals housed at +25 degrees C. It is concluded that brown adipose tissue from sarcoma-bearing mice could not account quantitatively for the host wasting in tumor-bearing mice housed at room temperature.