Effect of eicosapentaenoic acid, protein and amino acids on protein synthesis and degradation in skeletal muscle of cachectic mice.

Atrophy of skeletal muscle reduces both the quality and quantity of life of patients with cancer cachexia. Loss of muscle mass is thought to arise from a reduction in protein synthesis combined with an enhanced rate of protein degradation, and few treatments are available to counteract this process. Eicosapentaenoic acid (EPA) has been shown to attenuate the enhanced protein degradation, but to have no effect on protein synthesis. This study examines the effect of EPA combined with a protein and amino-acid supplementation on protein synthesis and degradation in gastrocnemius muscle of mice bearing the cachexia-inducing MAC16 tumour. Muscles from cachectic mice showed an 80% reduction in protein synthesis and about a 50-fold increase in protein degradation compared with muscles from nontumour-bearing mice of the same age and weight. Treatment with EPA (1 g kg(-1)) daily reduced protein degradation by 88%, but had no effect on protein synthesis. Combination of EPA with casein (5.35 g kg(-1)) also had no effect on protein synthesis, but when combined with the amino acids leucine, arginine and methionine there was almost a doubling of protein synthesis. The addition of carbohydrate (10.7 g kg(-1)) to stimulate insulin release had no additional effect. The combination involving the amino acids produced almost a doubling of the ratio of protein synthesis to protein degradation in gastrocnemius muscle over that of EPA alone. No treatment had a significant effect on tumour growth rate, but the inclusion of amino acids had a more significant effect on weight loss induced by the MAC16 tumour than that of EPA alone. The results suggest that combination therapy of cancer cachexia involving both inhibition of the enhanced protein degradation and stimulation of the reduced protein synthesis may be more effective than either treatment alone.

Effect of a protein and energy dense N-3 fatty acid enriched oral supplement on loss of weight and lean tissue in cancer cachexia: a randomised double blind trial.

AIM: N-3 fatty acids, especially eicosapentaenoic acid (EPA), may possess anticachectic properties. This trial compared a protein and energy dense supplement enriched with n-3 fatty acids and antioxidants (experimental: E) with an isocaloric isonitrogenous control supplement (C) for their effects on weight, lean body mass (LBM), dietary intake, and quality of life in cachectic patients with advanced pancreatic cancer. METHODS: A total of 200 patients (95 E; 105 C) were randomised to consume two cans/day of the E or C supplement (480 ml, 620 kcal, 32 g protein +/- 2.2 g EPA) for eight weeks in a multicentre, randomised, double blind trial. RESULTS: At enrolment, patients' mean rate of weight loss was 3.3 kg/month. Intake of the supplements (E or C) was below the recommended dose (2 cans/day) and averaged 1.4 cans/day. Over eight weeks, patients in both groups stopped losing weight (delta weight E: -0.25 kg/month versus C: -0.37 kg/month; p = 0.74) and LBM (Delta LBM E: +0.27 kg/month versus C: +0.12 kg/month; p = 0.88) to an equal degree (change from baseline E and C, p<0.001). In view of evident non-compliance in both E and C groups, correlation analyses were undertaken to examine for potential dose-response relationships. E patients demonstrated significant correlations between their supplement intake and weight gain (r = 0.50, p<0.001) and increase in LBM (r = 0.33, p = 0.036). Such correlations were not statistically significant in C patients. The relationship of supplement intake with change in LBM was significantly different between E and C patients (p = 0.043). Increased plasma EPA levels in the E group were associated with weight and LBM gain (r = 0.50, p<0.001; r = 0.51, p = 0.001). Weight gain was associated with improved quality of life (p<0.01) only in the E group. CONCLUSION: Intention to treat group comparisons indicated that at the mean dose taken, enrichment with n-3 fatty acids did not provide a therapeutic advantage and that both supplements were equally effective in arresting weight loss. Post hoc dose-response analysis suggests that if taken in sufficient quantity, only the n-3 fatty acid enriched energy and protein dense supplement results in net gain of weight, lean tissue, and improved quality of life. Further trials are required to examine the potential role of n-3 enriched supplements in the treatment of cancer cachexia.

Cachexia in MAC16 adenocarcinoma: suppression of hunger despite normal regulation of leptin, insulin and hypothalamic neuropeptide Y.

Weight loss normally stimulates hunger, through mechanisms that include falls in circulating leptin and insulin, leading to stimulation of hypothalamic neuropeptide Y (NPY). Here, we investigated the leptin, insulin and NPY to clarify why hunger is suppressed in mice with severe cachexia due to the MAC16 adenocarcinoma. MAC16-bearing mice progressively lost weight (19% below controls) and fat (- 61%) over 16 days after tumour transplantation, while total food intake fell by 10%. Pair-fed mice showed less wasting, with final weight being 9% and fat mass 25% below controls. Plasma leptin fell by 85% in MAC16 and 51% in pair-fed mice, in proportion to loss of fat. Plasma insulin was also reduced by 49% in MAC16 and 53% in pair-fed groups. Hypothalamic leptin receptor (OB-Rb) mRNA was significantly increased in both MAC16 (+ 223%) and pair-fed (+192%) mice. Hypothalamic NPY mRNA was also significantly raised in MAC16 (+152%) and pair-fed (+ 99%) groups, showing negative correlations with plasma leptin and insulin, and a positive association with OB-Rb mRNA. In MAC16-induced cachexia, leptin production and hypothalamic OB-Rb and NPY expression are regulated appropriately in response to fat depletion. Therefore, suppression of hunger is probably due to tumour products that inhibit NPY transport or release, or that interfere with neuronal targets downstream of NPY.

Effect of a fish oil-enriched nutritional supplement on metabolic mediators in patients with pancreatic cancer cachexia.

Weight loss in advanced cancer patients is refractory to conventional nutritional support. This may be due to metabolic changes mediated by proinflammatory cytokines, hormones, and tumor-derived products. We previously showed that a nutritional supplement enriched with fish oil will reverse weight loss in patients with pancreatic cancer cachexia. The present study examines the effect of this supplement on a number of mediators thought to play a role in cancer cachexia. Twenty weight-losing patients with pancreatic cancer were asked to consume a nutritional supplement providing 600 kcal and 2 g of eicosapentaenoic acid per day. At baseline and after 3 wk, patients were weighed and samples were collected to measure serum concentrations of interleukin (IL)-6 and its soluble receptor tumor necrosis factor receptors I and II, cortisol, insulin, and leptin, peripheral blood mononuclear cell production of IL-1 beta, IL-6, and tumor necrosis factor, and urinary excretion of proteolysis inducing factor. After 3 wk of consumption of the fish oil-enriched nutritional supplement, there was a significant fall in production of IL-6 (from median 16.5 to 13.7 ng/ml, P = 0.015), a rise in serum insulin concentration (from 3.3 to 5.0 mU/l, P = 0.0064), a fall in the cortisol-to-insulin ratio (P = 0.0084), and a fall in the proportion of patients excreting proteolysis inducing factor (from 88% to 40%, P = 0.008). These changes occurred in association with weight gain (median 1 kg, P = 0.024). Various mediators of catabolism in cachexia are modulated by administration of a fish oil-enriched nutritional supplement in pancreatic cancer patients. This may account for the reversal of weight loss in patients consuming this supplement.

Effect of oral eicosapentaenoic acid on weight loss in patients with pancreatic cancer.

Eicosapentaenoic acid (EPA) has been shown to modulate aspects of the inflammatory response that may contribute to weight loss in cancer. This study aimed to evaluate the acceptability and effects of oral supplementation with high-purity EPA in weight-losing patients with advanced pancreatic cancer. Twenty-six patients were entered into the study. EPA (95% pure) was administered as free acid starting at 1 g/day; the dose was increased to 6 g/day over four weeks, and then a maintenance dose of 6 g/day was administered. Patients were assessed before EPA and at 4, 8, and 12 weeks while receiving EPA, for weight, body composition, hematologic and clinical chemistry variables, acute-phase protein response, and performance status. Overall survival was noted. Supplementation was well tolerated, with only five patients experiencing side effects possibly attributable to the EPA. Before starting EPA, all patients had been losing weight at a median rate of 2 kg/mo. In general, after EPA supplementation, weight was stable. After four weeks of EPA supplementation, patients had a median weight gain of 0.5 kg (p = 0.0009 vs. rate of weight loss at baseline), and this stabilization of weight persisted over the 12-week study period. Total body water as a percentage of body weight remained stable, as did the proportion of patients with an acute-phase protein response, patients' nutritional intake, and performance status. Overall median survival from diagnosis in this study was 203 days. This study suggests that EPA is well tolerated, may stabilize weight in cachectic pancreatic cancer patients, and should be tested as an anticachectic agent in controlled trials.

The effect of an oral nutritional supplement enriched with fish oil on weight-loss in patients with pancreatic cancer.

Previous studies have suggested that administration of oral eicosapentaenoic acid (EPA) will stabilize weight in patients with advanced pancreatic cancer. The aim of the present study was to determine if a combination of EPA with a conventional oral nutritional supplement could produce weight gain in these patients. Twenty patients with unresectable pancreatic adenocarcinoma were asked to consume two cans of a fish oil-enriched nutritional supplement per day in addition to their normal food intake. Each can contained 310 kcal, 16.1 g protein and 1.09 g EPA. Patients were assessed for weight, body composition, dietary intake, resting energy expenditure (REE) and performance status. Patients consumed a median of 1.9 cans day(-1). All patients were losing weight at baseline at a median rate of 2.9 kg month(-1). After administration of the fish oil-enriched supplement, patients had significant weight-gain at both 3 (median 1 kg, P= 0.024) and 7 weeks (median 2 kg, P = 0.033). Dietary intake increased significantly by almost 400 kcal day(-1) (P = 0.002). REE per kg body weight and per kg lean body mass fell significantly. Performance status and appetite were significantly improved at 3 weeks. In contrast to previous studies of oral conventional nutritional supplements in weight-losing cancer patients, this study suggests that an EPA-enriched supplement may reverse cachexia in advanced pancreatic cancer.

The effect of polyunsaturated fatty acids on the progress of cachexia in patients with pancreatic cancer.

Cachexia is common in patients with pancreatic cancer and has been associated with persistent activation of the hepatic acute phase response and increased energy expenditure. Fatty acids have been shown to have anticachectic effects in animal models and to reduce inflammatory mediators in healthy subjects and patients with chronic inflammatory disease. Eighteen patients with unresectable pancreatic cancer received dietary supplementation orally with fish oil capsules (1 g each) containing eicosapentaenoic acid 18% and docosahexaenoic acid 12%. Anthropometric measurement, body composition analysis, and measurement of resting energy expenditure and serum C-reactive protein were performed before and after supplementation with a median of 12 g/day of fish oil. Patients had a median weight loss of 2.9 kg/month (IQR 2-4.6) prior to supplementation. At a median of 3 months after commencement of fish oil supplementation, patients had a median weight gain of 0.3 kg/month (IQR 0-0.5) (p < 0.002). Changes in weight were accompanied by a temporary but significant reduction in acute phase protein production (p < 0.002) and by stabilisation of resting energy expenditure. This study suggests a component fish oil, perhaps EPA, merits further investigation in the treatment of cancer cachexia.

Inhibition of lipolysis and muscle protein degradation by EPA in cancer cachexia.

Depletion of muscle and adipose tissue in cancer cachexia appears to arise not only from decreased food intake but also from the production of catabolic factors by certain tumours. Experiments with the cachexia-inducing MAC16 tumour in mice showed that when part of the carbohydrate calories were replaced by fish oil, host body weight loss was inhibited. The effect occurred without an alteration of either the total calorie consumption or nitrogen intake. Instead, one of the polyunsaturated fatty acids (PUFA) in fish oil, eicosapentaenoic acid (EPA), was found directly to inhibit tumour-induced lipolysis. The effect was structurally specific, as two related PUFA, docosahexaenoic acid (DHA) and gamma-linolenic acid (GLA), were without effect. The antilipolytic effect of EPA arose from an inhibition of the elevation of cyclic AMP in adipocytes in response to the lipid mobilizing factor. The increased protein degradation in the skeletal muscle of cachectic animals was also inhibited by EPA. This effect was due to the inhibition of the rise in muscle prostaglandin E2 in response to a tumour-produced proteolytic factor by EPA. Thus, reversal of cachexia by EPA in this mouse model results from its capacity to interfere with tumour-produced catabolic factors. Similar factors have been detected in human cancer cachexia.

Mechanism of lipid mobilization associated with cancer cachexia: interaction between the polyunsaturated fatty acid, eicosapentaenoic acid, and inhibitory guanine nucleotide-regulatory protein.

During a study of the mechanism of cancer cachexia, a debilitating condition in which catabolism of host muscle and adipose tissue occurs, it has been observed that the process can be effectively reversed in vivo by the polyunsaturated fatty acid, eicosapentaenoic acid (EPA), but not by other PUFA of either the n-3 or n-6 series. In vitro studies showed that EPA blocked the action of a tumour-produced catabolic factor at the level of the adipocyte, and that the effect of EPA also extended to beta-adrenergic stimuli and polypeptide hormones. Again the effect was specific to EPA and appeared to arise from an inhibition of the elevation of cyclic AMP levels in adipocytes in response to varied stimuli. Using isoprenaline stimulated lipolysis as a model system we have shown that EPA has a direct inhibitory effect on isoprenaline-stimulated adenylate cyclase in isolated plasma membrane fractions with half maximal inhibition at a concentration of 165 microM. The inhibitory effect was specific for EPA and was not shown by docosahexaenoic or arachidonic acids. The inhibitory effect of EPA on adenylate cyclase showed properties similar to hormonal inhibition of the enzyme in that it was (i) GTP-dependent, (ii) non-competitive with isoprenaline, (iii) eliminated following treatment of either adipocytes or plasma membrane fractions with pertussis toxin, which is known to ADP-ribosylate the alpha-subunit of an inhibitory guanine nucleotide-regulatory protein (Gi), thus leading to its inactivation. This suggests that inhibition of cyclic AMP formation by EPA was due, at least in part, to a Gi-mediated inhibition of adenylate cyclase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of megestrol acetate on weight loss induced by tumour necrosis factor alpha and a cachexia-inducing tumour (MAC16) in NMRI mice.

The effect of the synthetic progesterone, megestrol acetate, on weight loss induced by both tumour necrosis factor alpha (TNF) as a model for the cachexia accompanying the acquired immunodeficiency syndrome and by a cachexia-inducing tumour (MAC16) has been studied in NMRI mice. Megestrol acetate was effective in preventing weight loss in both model systems with treated animals having an increase in intake of both food and water. Megestrol acetate was unable to prevent loss of body weight in animals pair-fed with TNF treated animals, suggesting that the increase in food and water intake was responsible for the increase in body weight. Analysis of body composition showed that the major contribution to the increase in body weight in animals treated with megestrol acetate was an increase in water content, although there was also an increase in carcass fat in animals bearing the MAC16 tumour given the high dose of megestrol acetate. Animals bearing the MAC16 tumour had a significant increase in tumour weight after treatment with megestrol acetate, possibly owing to the increased plasma glucose levels. These results suggest that an increase in appetite and weight gain alone are not sufficient to justify the anticachectic effect of a particular agent and that body composition analysis and tumour growth rate are very important parameters.

Inhibition of weight loss by omega-3 fatty acids in an experimental cachexia model.

The effect of substitution of the carbohydrate component of the diet by calories derived from fish oil on host body weight loss and tumor growth rate has been studied in an experimental colon adenocarcinoma (MAC16). This tumor produces extensive host weight loss and reductions in both total body fat and muscle dry weight, without a reduction in food intake. Diets containing fish oil significantly reduced host body weight loss, with almost complete protection occurring when the fish oil comprised 50% of the calories, without an alteration of total calorie consumption or nitrogen intake. There was also a significant reduction in tumor growth rate, although the reduction in host weight loss was greater than might be expected from a smaller tumor burden. The reduction of host body weight loss was associated with an increase in total body fat and muscle mass. The effect appears specific to the type of fat since comparable results were not obtained with a gamma-linolenic acid-enriched diet. When compared with cyclophosphamide and 5-fluorouracil the fish oil diet exerted a similar antitumor effect at the maximum dose. Whereas the antitumor effect of the former agents was achieved with considerable host toxicity, the latter produced no toxicity and almost completely abolished the cachectic effect of the tumor. These results suggest that fish oil is a nontoxic, highly effective anticachectic agent with the added advantage of antitumor activity.

Changes in tRNA methyltransferase activity and cellular S-adenosylmethionine content following methionine deprivation.

Although homocysteine was unable to support growth of Walker carcinoma in media lacking methionine it did enable some proliferation of TLX5 lymphoma. In both cell lines there was an increase in growth rate in the presence of homocysteine at limiting methionine concentrations. The proliferation rate of Walker carcinoma was proportional to the methionine concentraion of the medium down to 0.5 microgram/ml, whereas growth of TLX5 lymphoma was only slightly reduced at such methionine concentrations. The difference in proliferative ability between the two cell lines was reflected in the level of S-adenosyl-L-methionine under conditions of methionine deprivation. In both cases transferance to a media in which methionine was growth limiting caused a rapid increase in the activity of tRNA methyltransferases to levels six to seven-fold greater than the control. The initial increase in methylase activity was not prevented by cycloheximide, although after 4 h there was a progressive decrease in activity which approached control values within 24 h. The increase in tRNA methyltransferase activity on removal of the normal level of methionine in the medium was also seen with human embryonic fibroblasts, which are able to proliferate normally in methionine-deficient, homocysteine-supplemented media. These results suggest that methyltransferase activity may be regulated in part by the S-adenosyl-methionine content of the cell.