Abnormal substrate metabolism and nutritional strategies in cancer management

Effects of simvastatin administration in an experimental model of cancer cachexia

OBJECTIVE

We evaluated whether statins, in view of their anti-inflammatory properties, may effectively prevent the onset or modulate the severity of muscle wasting during cancer cachexia.

METHODS

Simvastatin was administered to rats bearing the Yoshida AH-130 ascites hepatoma, a well-studied cytokine-dependent experimental model of cancer cachexia.

RESULTS

Quite surprisingly, the drug negatively affected the wasting pattern induced by the AH-130 hepatoma. In fact, the administration of simvastatin to tumor hosts induced a further weight reduction of all the tissues examined except for the soleus, in the absence of significant effects of simvastatin on tumor growth or on food intake. No effects were observed after simvastatin administration in control animals, with the exception of a significant (P < 0.05) reduction in heart weight.

CONCLUSIONS

Simvastatin administration, although capable of negatively modulating the inflammatory response, did not prevent muscle wasting in this experimental model of cancer cachexia. Moreover, the further muscle loss observed in simvastatin-treated tumor-bearing animals suggests that a note of caution should be introduced in treating cancer patients with statins in view of the possible occurrence of harmful side effects.

Anticytokine treatment prevents the increase in the activity of ATP-ubiquitin- and Ca(2+)-dependent proteolytic systems in the muscle of tumour-bearing rats

The ascites hepatoma Yoshida AH-130 induces loss of body weight and tissue waste. Tumour necrosis factor alpha (TNF-alpha) plays a pivotal role in the pathogenesis of muscle wasting in this model system, but other cytokines, such as interleukin-6, may be involved. In order to verify whether a combined anticytokine treatment may synergistically counteract muscle protein degradation, tumour bearing rats were treated with pentoxyfilline (PTX, an inhibitor of TNF-alpha synthesis), or with suramin (SUR, an antiprotozoal drug blocking the peripheral action of several cytokines including IL-6 and TNF-alpha), or both the drugs, and the effects on muscle proteolytic systems were assessed. Muscle protein loss in the AH-130-bearing rats was associated with increased activity of both the ATP-ubiquitin- and the calpain- dependent proteolytic pathways (246% and 230% of controls, respectively). Both PTX and SUR, either alone or in combination, prevented the depletion of muscle mass and significantly reduced the activity of muscle proteolytic systems. In particular, treatment with SUR, either alone or with PTX, induced a decrease in enzymatic activities to values similar to those of controls. The results obtained in the present paper demonstrate that: (i) muscle depletion in this model is indeed associated with increased proteasome- and calpain-dependent proteolysis, as previously suggested by increased mRNA expression of molecules pertaining to both pathways; (ii) anticytokine treatments effectively reduce muscle protein loss by down-regulating the activity of at least two major proteolitic systems; (iii) SUR is more effective than PTX in reducing the activity of proteolytic systems, possibly because of its multiple anticytokine action.

Abnormal liver metabolism in cancer patients detected by (31)P MR spectroscopy

There is accumulating evidence indicating that the presence of malignant disease is accompanied by profound changes of liver metabolism in the cancer-bearing host. We previously reported [P. C. Dagnelie, J. D. Bell, -S. C. R. Williams, T. E. Bates, P. D. Abel and C. S. Foster, Br. J. Cancer 67, 1303-1309 (1993)] marked (31)P MRS-detected alterations in phosphorylation status as well as in phospholipid and glucose metabolism in the liver of rats bearing Dunning prostate tumours. The aim of the present study was first to define abnormalities in liver metabolism in patients with a distant malignancy using (31)P MRS, and second to explore the value of including long-TR sequences in clinical (31)P MRS studies of the liver. Liver metabolite levels were expressed relative to total MR-detectable phosphate. In weight-losing (WL, n = 10), but not in weight-stable (WS, n = 13) cancer patients, liver phosphomonoester (PME) levels were significantly elevated, whereas phosphodiester (PDE) levels were reduced when compared with age-matched healthy subjects (n = 12). The TR 20:1 s ratio of PDE was increased in WS and WL cancer patients, suggesting longer T(1). At TR 20 s, but not at TR 1 s, ATP levels were significantly reduced in in WS and WL cancer patients compared with healthy subjects; similarly, P(i) levels were reduced in WL patients at TR 20 and 5s, but not at TR 1 s. ATP:P(i) ratios were unchanged regardless of TR. pH values increased in the order: healthy < cancer-WS < cancer-WL. The PME chemical shift had significantly moved downfield in cancer patients, reflecting increased contributions from glycolytic/gluconeogenic intermediates. The observed changes in PME are consistent with previous reports suggesting increased gluconeogenesis in the liver of patients with a distant malignant tumour. Furthermore, our data support the use of including long-TR sequences in clinical (31)P MRS liver studies.

Nutritional support of the hospitalized patient

Comprehensive care of patients in hospitals includes assessment of nutritional status and provision of appropriate support. This approach is facilitated by knowledge of the essential differences in metabolism between starved and stressed states. Nutritional assessment and care of patients in a hospital are based on answers to the following questions: Who gets it? When do they get it? How much do they get? What route is used to administer it? What kind do they get? What are common complications of enteral and parenteral support? What nutritional aspects are pertinent to common diseases?

Nutritional issues in cancer management

The objective of this article was to investigate the relationship between nutrition and cancer, as it relates to the initiation, promotion, and treatment of tumor growth. English-language studies published in the last 25 years were retrieved using MEDLINE, bibliographies, and consultation with experts. MEDLINE search terms included "cancer", "malnutrition," and "nutritional support." In vitro and in vivo controlled studies addressing the impact of nutritional factors on cancer prevention and treatment were selected. Approximately 30% of cancers in the Western countries are diet-related. The presence of malignancy affects patients' nutritional status negatively, leading to increased morbidity and mortality. Standard nutritional support (both enteral and parenteral) is not always effective in significantly improving outcome in malnourished cancer patients, due to characteristic changes in host metabolism. Preliminary studies suggest that newer nutritional-pharmacologic agents may be beneficial in counteracting the derangement of host metabolism, and consequently in ameliorating cancer patients' nutritional status and outcome of malnourishment. This review suggests that dietary manipulations and nutritional-pharmacologic therapy might be highly effective adjuncts in controlling the symptoms of patients with neoplastic disease.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Altered phosphorylation status, phospholipid metabolism and gluconeogenesis in the host liver of rats with prostate cancer: a 31P magnetic resonance spectroscopy study

31P magnetic resonance spectroscopy (MRS) in vivo and in vitro was used to study modulation of host liver (HL) metabolism in rats bearing the MAT-LyLu variant of the Dunning prostate tumour. Animals were inoculated either with 10(6) or 10(7) MAT-LyLu cells, or with saline to serve as controls. Carcass weight in tumour-bearing (TB) animals decreased despite similar food and water intake in both groups. Absence of metastatic tumour cells from HL of all TB animals was confirmed by histological examination. Twenty-one days after inoculation, 31P MRS showed a 2.5-fold increase in [Pi]/[ATP] ratios in HL in vivo (P < 0.001) which was confirmed by 31P MRS of liver extracts in vitro (P < 0.005). Phosphodiester to ATP ratios were significantly increased (P < 0.05) in HL in vivo, but absolute PDE levels were similar in both groups. Phosphomonoester to ATP ratios did not change, although absolute phosphomonoester levels in HL were reduced by -41% (not significant). In HL extracts in vitro, sharp reductions in the levels of glucose-6-phosphate (P < 0.05), fructose-6-phosphate (P = 0.05), phosphocholine (P < 0.001), glycerophosphocholine (P < 0.001), and glycerophosphoethanolamine (P < 0.001) were observed. Electron microscopy revealed increased amounts and altered distribution of rough endoplasmic reticulum in HL. These findings show that experimental prostate cancer significantly affects hepatic phosphorylation status, phospholipid metabolism, and gluconeogenesis in the host animal, and demonstrate the value of combined MRS in vivo and in vitro in monitoring HL metabolism in cancer.