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

Deprivation of glutamine in cell culture reveals its potential for treating cancer

The growth-stimulating capacity of calf serum (CS) in cell culture reaches a maximum of 10% with Balb 3T3 cells, remains at a plateau to 40% CS, and declines steeply to 100% CS. Growth capacity can be largely restored to the latter by a combination of cystine and glutamine. Glutamine is a conditionally essential amino acid that continues to function at very low concentrations to support the growth of nontransformed cells, but transformed cells require much larger concentrations to survive. These different requirements hold true over a 10-fold variation in background concentrations of CS and amino acids. The high requirement of glutamine for transformed cells applies to the development of neoplastically transformed foci. These observations have given rise to a novel protocol for cancer therapy based on the large difference in the need for glutamine between nontransformed and transformed cells. This protocol would stop the cumulative growth and survival of the transformed cells without reducing the growth rate of the nontransformed cells. The results call for studies of glutamine deprivation as a treatment for experimental cancer in rodents and clinical trials in humans.

Metabolic transformation in cancer

In 2000, Douglas Hanahan and Robert Weinberg published a review detailing the six hallmarks of cancer. These are six phenotypes that a tumour requires in order to become a fully fledged malignancy: persistent growth signals, evasion of apoptosis, insensitivity to anti-growth signals, unlimited replicative potential, angiogenesis and invasion and metastasis. However, it is becoming increasingly clear that these phenotypes do not portray the whole story and that other hallmarks are necessary: one of which is a shift in cellular metabolism. The tumour environment creates a unique collection of stresses to which cells must adapt in order to survive. This environment is formed by the uncontrolled proliferation of cells, which ignore the cues that would create normal tissue architecture. As a result, the cells forming the tumour are exposed to low oxygen and nutrient levels, as well as high levels of toxic cellular waste products, which is thought to propel cells towards a more transformed phenotype, resistant to cell death and pro-metastatic.

Stimulation of expression of the intestinal glutamine transporter ATB0 in tumor-bearing rats

BACKGROUND

Glutamine supplementation ameliorates host catabolic response in tumor bearing states. The purpose of this in vivo study was to investigate intestinal glutamine transport and expression of glutamine transporter ATB(0) in methyl-cholanthrene (MCA)-sarcoma bearing rats.

METHODS

Fisher-344 rats underwent subcutaneous flank implantation of MCA-sarcoma cells (saline as control) and were pair-fed an equal quantity of chow as controls, to account for tumor-induced anorexia, until tumors reached 10 or 20% body weight. Intestinal mucosal brush border membrane [3H]-Glutamine transport was measured. Glutamine transporter ATB(0) mRNA and protein levels were measured by real-time PCR and western blot techniques, respectively.

RESULTS

Glutamine transport activity across the intestinal brush border membrane (BBM) was 3.7-fold higher in tumor-bearing rats (TBR) than in controls (TBR 153 +/- 22.6 vs. Control 41.9 +/- 9.7 pmol/mg protein/10s, P < .01). Transporter ATB(0) mRNA levels were 1.4-fold higher in tumor-bearing rats (Relative value TBR .61 +/- .12 vs. Control .43 +/- .1, P < .05). A 1.4-fold increase in transporter ATB(0) protein levels was observed in the tumor-bearing rats (Relative value TBR .52 +/- .07 vs. Control .37 +/- .04, P < .05). Circulating aortic plasma glutamine levels were 1.3-fold higher in tumor bearing rats ([Glutamine] = .63 +/- .02 Control vs. [Glutamine] = .74 +/- .01 mmol/l TBR, P < .0001). Portal venous plasma glutamine levels were also higher in tumor bearing rats ([Glutamine] = .47 +/- .01 Control vs. [Glutamine] = .60 +/- .02 mmol/l TBR, P < .0001).

CONCLUSION

Intestinal brush border membrane glutamine transport activity, transporter ATB(0) mRNA and protein levels are up-regulate in tumor-bearing rats.

Naproxen, clenbuterol and insulin administration ameliorates cancer cachexia and reduce tumor growth in Walker 256 tumor-bearing rats

Cancer cachexia is characterized by anorexia and intense peripheral catabolism. We examine the potential benefits of combination of different anabolic agents such as insulin and clenbuterol associated to prostaglandin synthesis inhibitor (naproxen) on tumor growth, cachexia and renal function in Walker 256 tumor-bearing rats (WK). Groups were separated into WK, and WK with naproxen (WK N) or naproxen plus clenbuterol (WK NCb) or naproxen plus clenbuterol plus insulin (WK NCbI). Treatment begins at the 4th day after tumor inoculation, at the 14th day they were killed, glycemia, lacticidemia, glycogen content from liver, soleus and gastrocnemius muscles, tumor mass, body weight and kidney function were determined. Glycemia and glycogen content were reduced and lacticidemia increased in WK (p<0.05) as compared to control rats. The glycogen content recovered in all treated groups. Tumor weight was significantly reduced by the different treatments. At the 14th weight change (carcass-initial body weight) in the control increased by 38% and in the WK -2%. Naproxen treatment (WK N) induced an increased by 14%. The inclusion of clenbuterol (WK NCb) and insulin (WK NCbI) by 38 and 41%, respectively. Mean glomerular filtration rate (GFR) increased in the WK (p<0.05) as compared to control, but in the WK NCb the GFR was similar to control. Our results suggest that naproxen is able to reduce tumor growth and its association with insulin and clenbuterol induce mass weight gain and recovery energy fuel.

Effects of nandrolone propionate on experimental tumor growth and cancer cachexia

We studied the tumor host response to excessive doses of an anabolic steroid (nandrolone propionate, 2.5 mg 20 g intraperitoneally every second day for 11 days) with respect to body composition and tumor cell kinetics in MCG 101 sarcoma-bearing mice (C57BL/6J) with progressive cachexia. Although survival and food intake were not affected, a significant weight gain was observed that was essentially attributed to water retention. Net protein content was increased only to a minor extent (15%), of which only the liver accounted for a significant part of the body compartments. Hepatic protein accumulation was obviously caused by decreased protein degradation, since hepatic RNA content was unchanged. After anabolic steroid administration, reduced histochemical staining of succinate dehydrogenase was observed in skeletal muscles rich in oxidative type 1 fibers, but it was not different from that of tumor-bearing control animals, which was also confirmed by measurements of citrate synthase and cytochrome c oxidase activities in skeletal muscle and liver tissue. The anabolic steroid had no significant effect on tumor growth in terms of weight progression, energy state, polyamine synthesis rate, cell division rate, and cell cycle cytocompartments. We conclude that anabolic steroid supplementation is not therapeutically beneficial in counteracting progressive weight loss in experimental cancer.

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

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

Growth hormone, insulin, and somatostatin therapy of cancer cachexia

BACKGROUND

Cancer cachexia is associated with a decreased insulin:glucagon ratio. The authors hypothesized that the decrease in this anabolic hormone index is largely responsible for the progressive catabolism characteristic of cancer cachexia. Previous studies of insulin therapy alone in treating cancer cachexia have yielded limited success due to insulin-induced hypoglycemia and subsequent glucagon secretion. The current study was performed to determine the effect of combined hormone therapy (growth hormone, insulin, and somatostatin) on tumor growth, metastasis, and host metabolism.

METHODS

Twenty-four female Lewis/Wistar rats (175-200 g) were subcutaneously inoculated on the flank with the MAC-33 tumor, a spontaneously metastasizing mammary adenocarcinoma. Thirty days after tumor implantation, animals were randomized to receive combined hormone therapy or saline (control) injections. Hormone therapy consisted of recombinant growth hormone (1000 U/kg/day intraperitoneally [IP]), somatostatin analogue (SMS 201-995; 150 micrograms/kg twice daily IP) and NPH humulin insulin (5 U/kg twice daily subcutaneously).

RESULTS

Triple hormone therapy with growth hormone, insulin, and somatostatin significantly increased host carcass weight (211 +/- 4 g versus 179 +/- 6 g; P < 0.01) and decreased tumor:carcass ratio (0.25 +/- 0.03 versus 0.35 +/- 0.05; P < 0.01). Hamstring muscle weight and protein content were significantly increased and tumor cellular protein content was decreased in animals receiving triple hormone therapy. A significant decrease in S-phase tumor cell cycle kinetics occurred in hormone-treated versus control animals.

CONCLUSIONS

Thus, combined therapy of growth hormone, insulin, and somatostatin selectively supports host anabolism and inhibits tumor growth kinetics. Combined hormone therapy specifically improves skeletal muscle protein content and reduces tumor protein incorporation. This innovative metabolic therapy for cancer cachexia may be useful in the future to prevent the progressive catabolism present in the tumor-bearing host.

Parenteral vs enteral nutrition in tumor-bearing rats

The development of cachexia may complicate cancer therapy, yet controversy exists concerning its nutritional management. For example, use of total parenteral nutrition (TPN) may not be appropriate because of gut atrophy, possible stimulation of tumor growth, and lack of total host protein repletion. In the present experiment, host and tumor responses were compared after identical parenteral or enteral nutritional supplementation (EN). Eighteen days after subcutaneous inoculation of adult male Fischer-344 rats with fresh methylcholanthrene-induced sarcoma (tumor-bearing [TB] rats), catheters were placed into either the external jugular vein or the stomach. Four days later, rats were started on an 11-day course of either TPN or EN with a Freamine-III-based formula (amino acids = 6%, dextrose = 21.5%, lipid = 1.5%). When the rats were killed, there was no difference in tumor weight between the various TB groups. Carcass weight was increased significantly in both the TB-TPN and TB-EN groups, and there was an elevation in gastrocnemius protein content in both groups compared with the TB-rat food group. Small intestine protein was preserved in the TB-EN group to the level observed in the control-rat food animals. Total lipids in the liver were increased in both TB-TPN and TB-EN groups; however, the magnitude of the increase was less in the TB-EN animals. Neither treatment resulted in complete protein repletion of tumor-bearing rats. EN may be more appropriate than TPN in that gut mass is preserved. The maintenance of gut mucosa may prove to be beneficial in the treatment of the depleted, immunocompromised, and metabolically stressed host.

Glutamine and cancer

OBJECTIVE

This overview on glutamine and cancer discusses the importance of glutamine for tumor growth, summarizes the alterations in interorgan glutamine metabolism that develop in the tumor-bearing host, and reviews the potential benefits of glutamine nutrition in the patient with cancer.

SUMMARY BACKGROUND DATA

Glutamine is the most abundant amino acid in the blood and tissues. It is essential for tumor growth and marked changes in organ glutamine metabolism are characteristic of the host with cancer. Because host glutamine depletion has adverse effects, it is important to study the regulation of glutamine metabolism in cancer and to evaluate the impact of glutamine nutrition in the tumor-bearing state.

METHODS

Data from a variety of investigations on glutamine metabolism and nutrition related to the host with cancer were compiled and summarized.

RESULTS

Numerous studies on glutamine metabolism in cancer indicate that many tumors are avid glutamine consumers in vivo and in vitro. As a consequence of progressive tumor growth, host glutamine depletion develops and becomes a hallmark. This glutamine depletion occurs in part because the tumor behaves as a "glutamine trap" but also because of cytokine-mediated alterations in glutamine metabolism in host tissues. Animal and human studies that have investigated the use of glutamine-supplemented nutrition in the host with cancer suggest that pharmacologic doses of dietary glutamine may be beneficial.

CONCLUSIONS

Understanding the control of glutamine metabolism in the tumor-bearing host not only improves the knowledge of metabolic regulation in the patient with cancer but also will lead to improved nutritional support regimens targeted to benefit the host.

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

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

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.

Effects of increased beta 2-agonist dose in tumor-bearing animals

Cachexia and malnutrition are major contributing causes of significant morbidity and mortality in the cancer patient. Although supplemental nutrition alone does not reverse the cachectic process, the use of anabolic beta 2-adrenergic agonists in conjunction with supplemental nutrition does significantly reverse cachectic processes in tumor-bearing (TB) animals. To determine the most efficacious dose of the beta 2-agonist cimaterol (CIM), male Fischer-344 rats with dorsal subcutaneous methylcholanthrene sarcomas were maintained on supplemental enteral nutrition via surgically placed gastrostomy tubes. TB rats were given daily subcutaneous injections of either saline (Sal) or one of three doses of CIM for seven days. TB-Sal animals demonstrated significant cachexia with decreased extensor digitorum longus and gastrocnemius muscle dry weight and protein content. There was a significant increase in both extensor digitorum longus and gastrocnemius muscle dry weight and protein content in all treatment groups compared with TB controls. The greatest increase was in the 0.30 mg/kg CIM treatment group. Increased cardiac mass was associated with increasing dosage, with the greatest effect being observed in the 0.60 mg/kg CIM treatment group. This dosage, however, was associated with a decreased effect on muscle weight and protein content compared with the 0.30 mg/kg CIM dose. Thus the peak anabolic effect in TB animals was reached with the 0.30 mg/kg dose of CIM. Therefore, use of the beta 2-agonist CIM may prove useful in the treatment of cancer-induced cachexia.

Protein calorie malnutrition and cancer therapy

Anorexia and cachexia frequently complicate the late stages of malignancy and may be a prominent feature of early disease. The resulting weight loss often becomes a major focus of concern for the patient and the family and may significantly add to the morbidity and mortality of cancer. Factors which contribute to the wasting syndrome include the effects of the tumour, effects of chemotherapy, abnormalities of carbohydrate, fat and protein metabolism and the cytokine response. Administration of total parenteral nutrition (TPN) is an important method of addressing malnutrition, particularly in patients with nonfunctioning gastrointestinal tracts. A critical review of the TPN cancer literature is provided along with a discussion of new approaches and future directions in the nutritional support of patients with malignant disease, such as anabolic agents, hydrazine sulfate and megestrol.

The effects of glutamine-enriched total parenteral nutrition on tumor growth and host tissues

The effects of glutamine-enriched total parenteral nutrition (TPN+GLN) were studied in tumor-bearing rats because glutamine can benefit host tissues but also may stimulate tumor growth. Rats were implanted with the methylcholanthrene-induced fibrosarcoma (MCA sarcoma) and were studied when the tumor constituted less than 5% of carcass weight (small tumor) and when the tumor constituted 10% of carcass weight (large tumor). Provision of 20% of TPN protein as glutamine produced a significant increase in the arterial glutamine level and maintained the skeletal muscle intracellular glutamine concentration (2.02 +/- 0.1 versus 1.39 +/- 0.07 mumol/g, p less than 0.01). Concurrently, hindquarter GLN fractional release increased nearly threefold (p less than 0.05) in the TPN+GLN group. Glutamine-enriched total parenteral nutrition did not affect carcass weight, tumor weight, tumor DNA content, or tumor glutaminase activity. Furthermore, DNA flow cytometric analysis did not demonstrate any difference in percentage of aneuploid tumor cells within the G1, S, or G2M cell cycles. However, the ratio of aneuploid to diploid cells within the tumor mass increased by 20% in animals receiving glutamine. Glutamine-enriched total parenteral nutrition had no effect on tumor glutathione (GSH) levels. No increase in hepatic GSH levels was observed, but gut mucosal GSH levels were 20% greater in the TPN+GLN group (p less than 0.05). The provision of glutamine-enriched TPN may be beneficial to the host by maintaining skeletal muscle glutamine stores and by supporting gut GSH biosynthesis. In this tumor model, TPN+GLN does not appear to increase tumor size, tumor DNA content, or tumor glutamine metabolism, but the ratio of tumor cells to host infiltrating cells within the tumor mass appears to be increased.

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

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

Clenbuterol plus acivicin decrease tumor growth and increase muscle mass in rats maintained on total parenteral nutrition

Two problems associated with supplemental nutrition of tumor-bearing organisms are control of tumor growth and reduction of cachexia. To investigate these problems, rats bearing methylcholanthrene-induced sarcomas were maintained on total parenteral nutrition (TPN) for 10 to 12 days beginning 23 days after tumor inoculation. Combined treatment of one group of these rats with the glutamine antimetabolite, acivicin, and the beta 2-adrenergic agonist, clenbuterol, arrested tumor growth, increased skeletal muscle mass and protein content, increased gut mass, and decreased total plasma lipid levels. Resting energy expenditure and cardiac mass were increased by TPN and were increased further by acivicin plus clenbuterol. These results demonstrate that tumor growth and muscle wasting can be controlled during TPN of tumor-bearing organisms. Therefore, cachectic depletion of lean body tissue may not be obligatory in neoplastic disease.

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.