Fat metabolism and cancer

Circulating fatty acids in patients with head and neck cancer after treatment: an explorative study with a one-year perspective

BACKGROUND

Unintended weight loss and nutritional problems are often seen in patients with head and neck cancer, but changes in lipid metabolism are poorly studied.

AIM/OBJECTIVES

The present study aimed to explore the longitudinal changes in circulating fatty acid (FA) composition in patients with head and neck cancer.

MATERIALS AND METHODS

This study included 27 patients with head and neck cancer. Treatment consisted of single modality or combined modality treatments. The patients were assessed by repeated blood sampling and body weight assessments before treatment started and on three occasions after the start of treatment. FA profiling included gas chromatography analysis of unsaturated FAs and saturated FAs in serum.

RESULTS

The values of three fatty acids - FA 14:0, FA 18:3n3, and FA 20:3n6 - changed in a specific pattern over the course of the study and the change in FA 14:0 correlated with weight changes.

CONCLUSIONS AND SIGNIFICANCE

This study showed altered profiles of both saturated and unsaturated FAs. An improved understanding of the metabolic pathways in patients with head and neck cancer supports the development of better nutritional surveillance and nutritional treatments.

Moderate exercise training since adolescence reduces Walker 256 tumour growth in adult rats

KEY POINTS

Cancer growth, cell proliferation and cachexia index can be attenuated by the beneficial programming effect of moderate exercise training, especially if it begins in adolescence. Walker 256 tumour-bearing rats who started exercise training during adolescence did not revert the basal low glycaemia and insulinaemia observed before tumour cell inoculation. The moderate exercise training improved glucose tolerance and peripheral insulin sensitivity only in rats exercised early in adolescence. The chronic effects of our exercise protocol are be beneficial to prevent cancer cachexia and hold clear potential as a nonpharmacological therapy of insulin sensitization.

ABSTRACT

We tested the hypothesis that moderate exercise training, performed early, starting during adolescence or later in life during adulthood, can inhibit tumour cell growth as a result of changes in biometric and metabolic markers. Male rats that were 30 and 70 days old performed a treadmill running protocol over 8 weeks for 3 days week^-1 , 44 min day^-1 and at 55-65% V ̇ O 2 max . After the end of training, a batch of rats was inoculated with Walker 256 carcinoma cells. At 15 days after carcinoma cell inoculation, the tumour was weighed and certain metabolic parameters were evaluated. The data demonstrated that physical performance was better in rats that started exercise training during adolescence according to the final workload and V ̇ O 2 max . Early or later moderate exercise training decreased the cachexia index, cell proliferation and tumour growth; however, the effects were more pronounced in rats that exercised during adolescence. Low glycaemia, insulinaemia and tissue insulin sensitivity was not reverted in Walker 256 tumour-bearing rats who trained during adolescence. Cancer growth can be attenuated by the beneficial programming effect of moderate exercise training, especially if it begins during adolescence. In addition, improvement in glucose-insulin homeostasis might be involved in this process.

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.

Design and synthesis of emodin derivatives as novel inhibitors of ATP-citrate lyase

Aberrant cellular metabolism drives cancer proliferation and metastasis. ATP citrate lyase (ACL) plays a critical role in generating cytosolic acetyl CoA, a key building block for de novo fatty acid and cholesterol biosynthesis. ACL is overexpressed in cancer cells, and siRNA knockdown of ACL limits cancer cell proliferation and reduces cancer stemness. We characterized a new class of ACL inhibitors bearing the key structural feature of the natural product emodin. Structure-activity relationship (SAR) study led to the identification of 1d as a potent lead that demonstrated dose-dependent inhibition of proliferation and cancer stemness of the A549 lung cancer cell line. Computational modeling indicates this class of inhibitors occupies an allosteric binding site and blocks the entrance of the substrate citrate to its binding site.

Significantly fewer protein functional changing variants for lipid metabolism in Africans than in Europeans

Background

The disorders in metabolism of energy substances are usually related to some diseases, such as obesity, diabetes and cancer, etc. However, the genetic background for these disorders has not been well understood. In this study, we explored the genetic risk differences among human populations in metabolism (catabolism and biosynthesis) of energy substances, including lipids, carbohydrates and amino acids.

Results

Two genotype datasets (Hapmap and 1000 Genome) were used for this study. The genetic risks of protein functional changing variants (PFCVs) on genes involved in lipid, carbohydrate and amino acid metabolism were calculated using two genetic risk indices: the total number of PFCVs (Num) and the total possibly harmful score of PFCVs (R). Observations in these two genotype datasets consistently showed that Africans had lower genetic risk in lipid metabolism (both catabolic and biosynthetic processes) compared to Europeans. However this relationship was not observed in carbohydrate and amino acid metabolism.

Conclusions

Our results suggested that Africans had higher efficiency of utilizing lipids as energy substances than Europeans. In other words, lipids might be more preferred as energy substances in Africans than in Europeans.

Acetylation stabilizes ATP-citrate lyase to promote lipid biosynthesis and tumor growth

Increased fatty acid synthesis is required to meet the demand for membrane expansion of rapidly growing cells. ATP-citrate lyase (ACLY) is upregulated or activated in several types of cancer, and inhibition of ACLY arrests proliferation of cancer cells. Here we show that ACLY is acetylated at lysine residues 540, 546, and 554 (3K). Acetylation at these three lysine residues is stimulated by P300/calcium-binding protein (CBP)-associated factor (PCAF) acetyltransferase under high glucose and increases ACLY stability by blocking its ubiquitylation and degradation. Conversely, the protein deacetylase sirtuin 2 (SIRT2) deacetylates and destabilizes ACLY. Substitution of 3K abolishes ACLY ubiquitylation and promotes de novo lipid synthesis, cell proliferation, and tumor growth. Importantly, 3K acetylation of ACLY is increased in human lung cancers. Our study reveals a crosstalk between acetylation and ubiquitylation by competing for the same lysine residues in the regulation of fatty acid synthesis and cell growth in response to glucose.

Inhibition of lung cancer growth: ATP citrate lyase knockdown and statin treatment leads to dual blockade of mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K)/AKT pathways

ATP citrate lyase (ACL) catalyzes the conversion of cytosolic citrate to acetyl-CoA and oxaloacetate. A definitive role for ACL in tumorigenesis has emerged from ACL RNAi and chemical inhibitor studies, showing that ACL inhibition limits tumor cell proliferation and survival and induces differentiation in vitro. In vivo, it reduces tumor growth leading to a cytostatic effect and induces differentiation. However, the underlying molecular mechanisms are poorly understood and agents that could enhance the efficacy of ACL inhibition have not been identified. Our studies focus on non-small cell lung cancer (NSCLC) lines, which show phosphatidylinositol 3-kinase (PI3K)/AKT activation secondary to a mutation in the K-Ras gene or the EGFR gene. Here we show that ACL knockdown promotes apoptosis and differentiation, leading to the inhibition of tumor growth in vivo. Moreover, in contrast to most studies, which elucidate how activation/suppression of signaling pathways can modify metabolism, we show that inhibition of a metabolic pathway "reverse signals" and attenuates PI3K/AKT signaling. Additionally, we find that statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, which act downstream of ACL in the cholesterol synthesis pathway, dramatically enhance the anti-tumor effects of ACL inhibition, even regressing established tumors. With statin treatment, both PI3K/AKT and the MAPK pathways are affected. Moreover, this combined treatment is able to reduce the growth of EGF receptor resistant tumor cell types. Given the essential role of lipid synthesis in numerous cancers, this work may impact therapy in a broad range of tumors.

Gene expression profiling of peripheral blood cells for early detection of breast cancer

INTRODUCTION

Early detection of breast cancer is key to successful treatment and patient survival. We have previously reported the potential use of gene expression profiling of peripheral blood cells for early detection of breast cancer. The aim of the present study was to refine these findings using a larger sample size and a commercially available microarray platform.

METHODS

Blood samples were collected from 121 females referred for diagnostic mammography following an initial suspicious screening mammogram. Diagnostic work-up revealed that 67 of these women had breast cancer while 54 had no malignant disease. Additionally, nine samples from six healthy female controls were included. Gene expression analyses were conducted using high density oligonucleotide microarrays. Partial Least Squares Regression (PLSR) was used for model building while a leave-one-out (LOO) double cross validation approach was used to identify predictors and estimate their prediction efficiency.

RESULTS

A set of 738 probes that discriminated breast cancer and non-breast cancer samples was identified. By cross validation we achieved an estimated prediction accuracy of 79.5% with a sensitivity of 80.6% and a specificity of 78.3%. The genes deregulated in blood of breast cancer patients are related to functional processes such as defense response, translation, and various metabolic processes, such as lipid- and steroid metabolism.

CONCLUSIONS

We have identified a gene signature in whole blood that classifies breast cancer patients and healthy women with good accuracy supporting our previous findings.

The causes and consequences of cancer-associated malnutrition

Cancer-associated malnutrition can result from local effects of a tumour, the host response to the tumour and anticancer therapies. Although cancer patients often have reduced food intake (due to systemic effects of the disease, local tumour effects, psychological effects or adverse effects of treatment), alterations in nutrient metabolism and resting energy expenditure (REE) may also contribute to nutritional status. Several agents produced by the tumour directly, or systemically in response to the tumour, such as pro-inflammatory cytokines and hormones, have been implicated in the pathogenesis of malnutrition and cachexia. The consequences of malnutrition include impairment of immune functions, performance status, muscle function, and quality of life. In addition, responses to chemotherapy are decreased, chemotherapy-induced toxicity and complications are more frequent and severe, and survival times are shortened. Depression, fatigue and malaise also significantly impact on patient well-being. In addition, cancer-related malnutrition is associated with significant healthcare-related costs. Nutritional support, addressing the specific needs of this patient group, is required to help improve prognosis, and reduce the consequences of cancer-associated nutritional decline.

Cancer-associated malnutrition

Malnutrition is a common problem among patients with cancer, affecting up to 85% of patients with certain cancers (e.g. pancreas). In severe cases, malnutrition can progress to cachexia, a specific form of malnutrition characterised by loss of lean body mass, muscle wasting, and impaired immune, physical and mental function. Cancer cachexia is also associated with poor response to therapy, increased susceptibility to treatment-related adverse events, as well as poor outcome and quality of life. Cancer cachexia is a complex, multifactorial syndrome, which is thought to result from the actions of both host- and tumour-derived factors, including cytokines involved in a systemic inflammatory response to the tumour. Early intervention with nutritional supplementation has been shown to halt malnutrition, and may improve outcome in some patients. However, increasing nutritional intake is insufficient to prevent the development of cachexia, reflecting the complex pathogenesis of this condition. Nutritional supplements containing anti-inflammatory agents, for example the polyunsaturated fatty acid (PUFA) eicosapentanoic acid (EPA), have been shown to be more beneficial to malnourished patients than nutritional supplementation alone. EPA has been shown to interfere with multiple mechanisms implicated in the pathogenesis of cancer cachexia, and in clinical studies, has been associated with reversal of cachexia and improved survival.

Interleukin-1 alpha promotes tumor growth and cachexia in MCF-7 xenograft model of breast cancer

Progression of breast cancer involves cross-talk between epithelial and stromal cells. This cross-talk is mediated by growth factors and cytokines secreted by both cancer and stromal cells. We previously reported expression of interleukin (IL)-1 alpha in a subset of breast cancers and demonstrated that IL-1 alpha is an autocrine and paracrine inducer of prometastatic genes in in vitro systems. To understand the role of IL-1 alpha in breast cancer progression in vivo, we studied the growth of MCF-7 breast cancer cells overexpressing a secreted form of IL-1 alpha (MCF-7IL-1 alpha) in nude mice. MCF-7IL-1 alpha cells formed rapidly growing estrogen-dependent tumors compared to parental cells. Interestingly, IL-1 alpha expression alone was not sufficient for metastasis in vivo although in vitro studies showed induction of several prometastatic genes and matrix metalloproteinase activity in response to cross-talk between IL-1 alpha-expressing cancer cells and fibroblasts. Animals implanted with MCF-7IL-1 alpha cells were cachetic, which correlated with increased leptin serum levels but not other known cachexia-inducing cytokines such as IL-6, tumor necrosis factor, or interferon gamma. Serum triglycerides, but not blood glucose were lower in animals with MCF-7IL-1 alpha cell-derived tumors compared to animals with control cell-derived tumors. Cachexia was associated with atrophy of epidermal and adnexal structures of skin; a similar phenotype is reported in triglyceride-deficient mice and in ob/ob mice injected with leptin. Mouse leptin-specific transcripts could be detected only in MCF-7IL-1 alpha cell-derived tumors, which suggests that IL-1 alpha increases leptin expression in stromal cells recruited into the tumor microenvironment. Despite increased serum leptin levels, animals with MCF-7IL-1 alpha cell-derived tumors were not anorexic suggesting only peripheral action of tumor-derived leptin, which principally targets lipid metabolism. Taken together, these results suggest that cancer cell-derived cytokines, such as IL-1 alpha, induce cachexia by affecting leptin-dependent metabolic pathways.

Paraneoplastic syndromes

The importance of paraneoplastic syndromes is often underestimated in the horse. Clinically, paraneoplastic syndromes can cause greater morbidity than the actual physical presence of the malignant tumor. The appearance may be the first sign of a malignancy and may be so severe that appropriate therapy for the underlying cancer is not initiated. This article reviews some of the most common paraneoplastic syndromes that are likely to occur in the horse.

Interventional nutrition for the cancer patient

Dogs and cats with cancer have significant alterations in carbohydrate, protein, and fat metabolism, which can result in cancer cachexia and subsequently can decrease quality of life, reduce response to therapy, and shorten survival time. Nutritional modulation may be beneficial in the treatment of cancer patients to reverse these metabolic alterations. There is evidence that foods relatively low in simple carbohydrates with moderate amounts of high-quality protein, fiber, and fat (especially fats of the omega-3 fatty acid series) are beneficial for pets with cancer. In addition, certain supplemental nutrients may have potential to reduce the risk of developing cancer, or the growth and metastases of established malignant disease. Nutritional intervention can be a powerful tool for controlling malignant disease and for reducing toxicity associated with chemotherapy and radiation therapy.

Nutritional and immunologic evaluation of patients with gastric cancer before and after surgery

The main objective was to evaluate a patient's immunologic and nutritional status as a prognostic indicator of morbidity and mortality in patients with gastric cancer. A prospective clinical study carried out at the National Cancer Institute in Bogotá, Colombia. Our study group consisted of 40 patients with a diagnosis of gastric adenocarcinoma that was treated surgically. Blood samples were taken before and 5 d after surgery; mononuclear cell typing was done by flow cytometry allowing a bicolor analysis. Nutritional evaluation was obtained through measurement of albumin levels, average weight loss, and nutritional risk index (NRI). Half of the malignancies were localized to the middle and lower third of the stomach: stage I, 17.55%; stage II, 10%; stage III, 55%; and stage IV, 17.5%. Twenty subtotal gastrectomies, 11 total gastrectomies, 7 gastrojejunostomies, and 2 esophagogastrectomies with D1 and D2-D3 lymph node resection were performed. A postoperative morbidity of 22.5% and a mortality of 7.5% were observed. A preoperative cellular immunosuppression was identified, with a helper lymphocyte (CD4) to suppressor/cytotoxic lymphocyte (CD8) ratio of 1.38 normal value (NV > 1.5), which increased according to the stage of the disease. Patients who died presented with a significantly greater preoperative cellular immunosuppression than those who survived (P = 0.05). Postoperative mortality correlated significantly with hypoalbuminemia (P = 0.008). In those who died, weight loss was greater than in those who survived (P = 0.06). Patients with severe malnutrition had greater postoperative mortality according to the NRI. Severe preoperative cellular immunosuppression (CD4/CD8 < 1), hypoalbuminemia, weight loss, and severe NRI have a positive predictive value for mortality in patients with gastric cancer.

Dietary lipids and calorie restriction affect mammary tumor incidence and gene expression in mouse mammary tumor virus/v-Ha-ras transgenic mice

We have studied the effects of food restriction (FR) and substitution of fish oil (FO; omega 3) for corn oil (CO; omega 6) on breast tumor incidence and survival in mouse mammary tumor virus/v-Ha-ras transgenic (Onco) mice. The diets were as follows: group 1, 5% (wt/wt) CO fed ad libitum (AL); group 2, 5% CO, restricted calories (40% fewer calories than AL; FR); group 3, 20% CO fed AL; and group 4, 20% FO fed AL. After 3 years, 40% of FR Onco (group 2) mice were alive, whereas there were no survivors in the other three groups. Similarly, tumor incidence was reduced to 27% (5 out of 18) in FR animals (group 2), whereas it was 83% (11 out of 13) in group 1 mice, 89% (16 out of 18) in group 3 mice, and 71% (10 out of 14) in group 4 mice. These protective effects of FR on survival and tumor incidence were paralleled by higher expression of the tumor suppressor gene p53 (wild type) and free-radical scavenging enzymes (catalase and superoxide dismutase) in breast tumors. Immunoblotting showed less ras gene product, p21, and increased p53 levels in the tumors of FR mice. In addition, FR decreased RNA levels of c-erbB-2, interleukin 6, and the transgene v-Ha-ras in tumors. In contrast, analysis of hepatic mRNA from tumor-bearing FR mice revealed higher expression of catalase, glutathione peroxidase, and superoxide dismutase. Survival and tumor incidence were not influenced significantly by dietary supplementation with FO in place of CO. Taken together, our studies suggest that moderate restriction of energy intake significantly inhibited the development of mammary tumors and altered expression of cytokines, oncogenes, and free-radical scavenging enzymes.

Acute metabolic effects of human recombinant tumor necrosis factor beta in the rat

BACKGROUND

Cancer cachexia is associated with several alterations in host metabolism, including hypoaminoacidemia and an increase in gluconeogenesis (GLC) and lipolysis. Tumor necrosis factor beta (TNF beta), a lymphokine released by mitogen-activated T lymphocytes and several cancer cell lines, causes an increase in lipolysis in 3T3L1 adipocytes. Since little is known about the metabolic effects of TNF beta in vivo, we examined its acute effects in the rat.

METHODS

Twenty-eight male Fischer rats were injected intraperitoneally with TNF beta (250 micrograms/kg) or saline (CTL), and after 4 h, isolated hepatocytes were obtained (by in situ collagenase liver perfusion [n = 12]) or aortic blood was collected (n = 16). Hepatocytes were incubated with 10 mM alanine (ALA) or 10 mM lactate (LAC), and glucose production was measured. Rates of GLC (nmol glucose/10(6) cells/min) were determined by linear regression. Plasma lactate, glucose, insulin, and amino acids (AA) (nmol/ml) were measured, and values were expressed as means +/- SEM. Comparisons between groups were made by unpaired t test or Mann-Whitney U test, and significance was defined as p < 0.05.

RESULTS

TNF beta caused a 130% increase in gluconeogenesis from alanine (2.7 +/- 0.5 vs 1.2 +/- 0.2 nmol glucose/10(6) cells/min, TNF vs CTL), and a 60% increase from lactate (7.5 +/- 1.0 vs 4.6 +/- 0.5 nmol glucose/10(6) cells/min, TNF vs CTL). Plasma insulin levels in TNF treated rats were 1.2 +/- 0.2 ng/ml compared to 1.1 +/- 0.2 ng/ml in CTL. Total amino acid levels in TNF treated rats were 3,175 +/- 111 nmol/ml compared to 3,190 +/- 103 nmol/ml in CTL.

CONCLUSION

In vivo TNF beta causes an increase in hepatic gluconeogenesis from alanine and lactate with no change in plasma insulin or amino acids.

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.

Alterations in lipoprotein profiles in dogs with lymphoma

After a 12-hour fast, blood samples were obtained from 31 dogs with previously untreated lymphoma. Blood samples were also collected from 16 of these dogs after up to 5 treatments with doxorubicin (30 mg/m2 intravenously every 3 weeks). All 16 dogs underwent complete remission. Five dogs were re-evaluated after relapse and after overt signs of cancer cachexia had become clinically apparent. Samples were assayed for 8 quantitative parameters: total cholesterol (T-CH) and total triglyceride (T-TG) concentrations, and the concentration of cholesterol and triglyceride in each of the three major lipoprotein fractions, very-low-density lipoprotein (LDL-CH and LDL-TG), and high-density lipoprotein (HDL-CH and HDL-TG). The results were compared with those from 20 healthy control dogs of similar weight and age before and 3 weeks after being given one dose of doxorubicin (30 mg/m2 intravenously). The administration of doxorubicin to control dogs resulted in a significant (P < .05) decrease in T-CH, LDL-CH, and HDL-CH, as well as a significant increase in VLDL-TG and HDL-TG. When compared with untreated controls, untreated dogs with lymphoma had significantly higher concentrations of VLDL-CH, T-TG, VLDL-TG, LDL-TG, and HDL-TG, and significantly lower concentrations of HDL-CH. HDL-TG and VLDL-TG concentrations from dogs with lymphoma were significantly increased above pretreatment values after relapse and development of overt signs of cancer cachexia.(ABSTRACT TRUNCATED AT 250 WORDS)

Energy expenditure in dogs with lymphoma fed two specialized diets

BACKGROUND

Cancer-caused cachexia has been reported to be caused in part by an increase in energy expenditure, and diets with nutrient profiles containing 30-50% nonprotein calories as fat instead of carbohydrate may exacerbate this state of inefficient energy utilization.

METHODS

Indirect calorimetry was performed on 22 dogs with high-grade lymphoblastic lymphoma that were randomized into a blind study and fed isocaloric amounts of a high-fat diet (Diet A) or a high-carbohydrate diet (Diet B) before and after remission was attained with up to five doses of doxorubicin chemotherapy (30 mg/m2 intravenously). Indirect calorimetry was also performed on 30 normal dogs for comparison.

RESULTS

During the initial evaluation period, the resting energy expenditure (REE/kg0.75, P < 0.05) and respiratory quotient (RQ, P < 0.05) were significantly lower than in the controls. Six weeks after the start of the study, the REE/kg0.75 and oxygen consumption (VO2/kg0.75) were significantly (P < 0.05) lower in both groups of dogs with lymphoma compared with the controls. The RQ determined 6 weeks after the start of the study for the dogs fed Diet A was significantly (P < 0.05) lower compared with that in the controls evaluated at the same time. When the two groups of dogs with lymphoma were compared with each other, there was no significant difference in any of the outcomes. The REE/kg0.75 and VO2/kg0.75 values were significantly lower (P < 0.05) in the group fed Diet A after the third evaluation period compared with the second evaluation. The REE/kg0.75 and VO2/kg0.75 values were significantly lower (P < 0.05) in the group given Diet B at the fourth evaluation period compared with the fifth.

CONCLUSIONS

These data suggest that energy expenditure of dogs with lymphoma decreases transiently in response to chemotherapy and remission, but these values are less than those determined in normal dogs and not altered significantly by diet.

Increased expression of the mRNA for hormone-sensitive lipase in adipose tissue of cancer patients

The expression of genes coding for regulatory enzymes involved in the uptake, synthesis and mobilisation of lipid was measured in adipose tissue of cancer patients. Total RNA was isolated from subcutaneous adipose tissue of control and cancer patients and the various mRNAs measured by Northern blot analysis. The total lipoprotein lipase enzymic activity and the relative levels of the mRNAs for lipoprotein lipase and for fatty acid synthase were not significantly different between cancer patients and control patients. However, there was a significant two-fold increase in the relative level of mRNA for hormone-sensitive lipase (HSL) in adipose tissue of cancer patients compared with control patients. The cancer patients also exhibited a two-fold elevation in serum triacylglycerol levels and serum free fatty acid levels. There was a significant correlation between the serum free fatty acid level and expression of HSL mRNA in the adipose tissue. The serum levels of insulin and tumour necrosis factor-alpha were not different between cancer and control patients. The results suggest that at least one of the mechanisms for depletion of lipid from adipose tissue in cancer patients operates at the level of increased expression of mRNA of the lipolytic regulatory enzyme, hormone-sensitive lipase.

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.

Alteration of serum and urinary lipolytic activity with weight loss in cachectic cancer patients

The possibility that weight loss in cancer patients may be augmented by tumour produced catabolic factors, which stimulate lipid mobilisation, was investigated in a group of cancer patients with total body weight loss ranging from 0 to 50%. The serum and urine lipolytic activity has been determined using freshly isolated murine adipocytes in an in vitro assay. As a control group, we have used patients with Alzheimer's disease, in which some patients may lose a considerable amount of weight, without an obvious cause. The serum lipolytic activity for the Alzheimer's group with weight loss (0.11 +/- 0.02 mumols glycerol released 10(5) adipocytes-1 ml-1 serum) was not significantly different from the group without weight loss (0.11 +/- 0.02 mumols glycerol released 10(5) adipocytes-1 ml-1) or from a healthy control group (0.07 +/- 0.02 mumols glycerol released 10(5) adipocytes-1 ml-1), but all three groups were significantly (P less than 0.005) lower than the cancer patient group (0.20 +/- 0.03 mumols glycerol 10(5) adipocytes-1 ml-1), irrespective of weight loss. A similar difference between the cancer and the control group was observed for the urinary lipolytic activity (0.67 +/- 0.03 versus 0.28 +/- 0.03 mumols glycerol released 10(5) adipocytes-1 mg creatinine-1 respectively, P less than 0.01). Weight loss in animals bearing the MAC16 adenocarcinoma was paralleled by a corresponding rise in serum lipolytic activity which peaked when the loss of carcass weight was 16%. A similar decrease in serum lipolytic activity was also observed in cancer patients at high percentages loss in body weight. However, a linear relationship was observed between both the serum and urinary lipolytic activity and weight loss in cancer patients (correlation coefficients 0.79 and 0.70 respectively) when the total body weight loss did not exceed 20%. This suggests that weight loss in cancer patients may be attributed, at least in part, to an, as yet, unidentified lipolytic factor.

Nutrition and cancer. Recent developments

Cancer cachexia is a complex syndrome that results in involuntary weight loss, even in the face of adequate nutritional intake. The profound metabolic abnormalities associated with cancer cachexia affect a large percentage of animals with cancer even before any clinical signs are seen. This paraneoplastic syndrome results in alterations in carbohydrate, lipid, and protein metabolism that, if left untreated, decrease the animal's quality of life and lead to a poor response to cancer therapy. An understanding of the metabolic abnormalities associated with cancer cachexia is of paramount importance to the practicing veterinarian to determine an accurate prognosis and to choose the optimal type of intravenous fluids and nutritional therapy for each patient. Although research identifying the optimal diet for cancer-bearing dogs and cats is still underway, some general principles apply. The first is that the patient should receive nutritional elements orally whenever possible. When oral feeding is not possible, nasogastric, gastrostomy, and jejunostomy tube feeding are viable options. When feeding by the gastrointestinal tract is not possible, parenteral feeding is a practical alternative.