Cancer and protein metabolism

Role of pyroglutamic acid in cumulus cells of women with polycystic ovary syndrome

PURPOSE

Polycystic ovary syndrome is a complex heterogeneous endocrine disorder associated with established metabolic abnormalities and is a common cause of infertility in females. Glutathione metabolism in the cumulus cells (CCs) of women with PCOS may be correlated to the quality of oocytes for infertility treatment; therefore, we used a metabolomics approach to examine changes in CCs from women with PCOS and oocyte quality.

METHODS

Among 135 women undergoing fertility treatment in the present study, there were 43 women with PCOS and 92 without. CCs were collected from the two groups and levels of pyroglutamic acid were measured using LC-MS/MS followed by qPCR and Western blot analysis to examine genes and proteins involved in pyroglutamic acid metabolism related to glutathione synthesis.

RESULTS

Women with PCOS showed increased levels of L-pyroglutamic acid, L-glutamate, and L-phenylalanine and decreased levels of Cys-Gly and N-acetyl-L-methionine. Gene expression of OPLAH, involved in pyroglutamic synthesis, was significantly increased in women with PCOS compared with those without. Gene expression of GSS was significantly decreased in women with PCOS and synthesis of glutathione synthetase protein was decreased. Expression of nuclear factor erythroid 2-related factor 2, involved in resistance to oxidative stress, was significantly increased in women with PCOS.

CONCLUSIONS

CCs of women with PCOS showed high concentrations of pyroglutamic acid and reduced glutathione synthesis, which causes oxidative stress in CCs, suggesting that decreased glutathione synthesis due to high levels of pyroglutamic acid in CCs may be related to the quality of oocytes in women with PCOS.

Dual Effects of High Protein Diet on Mouse Skin and Colonic Inflammation

Chronic inflammation is a major etiology of cancer. Accumulating epidemiological and experimental evidences suggest that intake of high protein diet (HPD) is associated with colitis-associated colon cancer, however, most of the studies were confined in colon. Systemic influence of HPD on inflammation indices in different tissues of an organism has never been studied. We therefore investigated the effect of HPD on mouse skin and colonic inflammation using the well characterized inflammation induction protocol in both tissues (12-O-tetradecanoylphorbol-13-acetate [TPA] for skin and dextran sodium sulfate [DSS] for colon). ICR mice were grouped to normal diet (ND, 20% casein) or HPD (50% casein) groups. In each diet group, mice were treated with either vehicle (acetone or H₂O), TPA, TPA and DSS, or DSS. Experimental diet was fed for total 4 weeks. After 1 week of diet feeding, 6.5 nmol of TPA was topically applied twice a week for 2 weeks on the shaved mouse dorsal skin. Drinking water containing 2% DSS was administered for 7 days at the final week of experiment. The results showed that TPA-induced skin hyperplasia, epidermal cell proliferation, and cyclooxygenase-2 (COX-2) expression were reduced in HPD group compared to ND group. In contrast, HPD increased DSS-induced colon mucosal hyperplasia, colonocyte proliferation, COX-2 expression, and plasma nitric oxide compared to ND group. This suggests that HPD exerts differential effect on different tissue inflammation which implies efficacy of protein intervention to human also should be monitored more thoroughly.

Nutritional status at diagnosis in children with cancer I. An assessment by dietary recall--compared with body mass index and body composition measured by dual energy X-ray absorptiometry

The nutritional status of children with cancer is clinically important. In an effort to separate the influences of disease and treatment, we studied children at the time of diagnosis. A total of 99 children underwent assessment by 24 hours dietary recall, measurement of body mass index (BMI), and analysis of body composition by dual energy x-ray absorptiometry (DXA scan). The group averages for calorie intake and BMI were close to the median population norms but ranged widely among individuals. As a group the study participants exceeded the Dietary Reference Intake for protein. Nine children (9%) had a BMI <fifth percentile. There were statistically significant but at best moderate correlations between dietary intake and body composition by DXA scan. Twenty-four hours dietary recall may not provide accurate assessment of nutritional status in individual children with cancer at diagnosis. However, DXA scans cannot be undertaken in a timely fashion on all children at this point. Alternative methods of assessment are being explored.

Plasma free amino acid profile in cancer patients

Redistribution or translocation of plasma free amino acids (PFAAs) to support visceral or tumor protein synthesis is an essential feature in cancer patients. An abnormal PFAA profile might be presented via the total reflection of cancer-induced protein metabolism in tumors, skeletal muscle and the liver in cancer patients. Clinical data from 13 studies have demonstrated a cancer-related PFAA profile, especially in digestive organ cancers. The PFAA profile can differ between the early and late stages of cancer. The profile is also affected by the type of cancer. Therefore, it is postulated that a detailed analysis of the PFAA profile may serve as one of the biological markers for cancer patients.

Serum creatinine: a surrogate measurement of lean body mass in children with acute lymphoblastic leukemia

BACKGROUND

Since creatinine is formed almost exclusively in skeletal muscle, the hypothesis of a relationship between serum creatinine (SC) and lean body mass (LBM), determined by dual-energy X-ray absorptiometry (DXA), was tested.

METHODS

Two cohorts of patients were analyzed: 37 children with acute lymphoblastic leukemia (ALL) and 20 children with primary muscular disorders (PMD). The latter cohort was used as a comparative group. Statistical analyses were performed using linear regressions.

RESULTS

A strong correlation was demonstrated between SC and LBM in the patients with PMD (r = 0.77) and in patients with ALL (r = 0.83 at diagnosis; r = 0.77 on therapy; and r = 0.56 off therapy). The correlation between SC and body size (body mass index) was much weaker (r = 0.38; r = -0.09; r = 0.29 at the successive observations in the ALL cohort and r = 0.05 in the PMD cohort). These data provide support for the initial hypothesis.

CONCLUSIONS

Further investigations with a wider variety of diseases are needed for this will allow the consideration of SC as a general surrogate measure of LBM and consequently of nutritional status.

Children, cancer, and nutrition--A dynamic triangle in review

The overall cure rate for cancer in childhood now exceeds 70% and is projected to reach 85% by the year 2010 in industrialized countries. Therefore, major attention is being placed on reducing the side effects of therapy. However, 85% of the world's children live in developing countries, where access to adequate care often is limited and health status frequently is influenced adversely by prevalent infectious diseases and malnutrition. Despite several confounding factors (different definitions of nutritional status, the wide variety of measures used for its assessment, the selection biases by disease and stage, treatment protocols of variable dose intensity and efficacy, small sample sizes of the studies conducted in the last 20 years), it is accepted that the prevalence of malnutrition at diagnosis averages 50% in children with cancer in developing countries; whereas, in industrialized countries, it is related to the type of tumor and the extent of the disease, ranging from < 10% in patients with standard-risk acute lymphoblastic leukemia to 50% in patients with advanced neuroblastoma. The importance of nutritional status in children with cancer is related to its possible influence on the course of the disease and survival. Some authors have described decreased tolerance of chemotherapy associated with altered metabolism of antineoplastic drugs, increased infection rates, and poor clinical outcome in malnourished children. In this article, the authors review methods of nutritional assessment and the pathogenesis of nutritional morbidity in children with cancer as well as correlations of nutritional status with diagnosis, treatment, and outcome.

Muscle wasting

The loss of lean body mass (muscle wasting) is initiated by cascades or events that precipitate increased proteolysis. Muscle wasting is stimulated by internal and external factors. Humorally related feedback loops stimulated by disease states, e.g., cancer, inflammatory myopathies, leukemia, or sepsis, and initiated as a response to systemic inflammatory response syndrome can cause a downward progression of events, resulting in chronic illness or even death. This article discusses the pathogenesis of muscle wasting, which is often referred to as cachexia.

Metabolic alterations in dogs with osteosarcoma

OBJECTIVE

To evaluate changes in resting energy expenditure (REE) as well as protein and carbohydrate metabolism in dogs with osteosarcoma (OSA).

ANIMALS

15 weight-stable dogs with OSA that did not have other concurrent metabolic or endocrine illness and twelve 1-year-old sexually intact female Beagles (control dogs).

PROCEDURES

Indirect calorimetry was performed on all dogs to determine REE and respiratory quotient (RQ). Stable isotope tracers (15N-glycine, 4.5 mg/kg of body weight, IV; 6,6-deuterium-glucose, 4.5 mg/kg, IV as a bolus, followed by continuous-rate infusion at 1.5 mg/kg/h for 3 hours) were used to determine rate of protein synthesis and glucose flux in all dogs. Dual-energy x-ray absorptiometry (DEXA) scans were performed to determine total body composition.

RESULTS

Accounting for metabolic body size, REE in dogs with OSA was significantly higher before and after surgery, compared with REE of healthy control dogs. The RQ values did not differ significantly between groups. Dogs with OSA also had decreased rates of protein synthesis, increased urinary nitrogen loss, and increased glucose flux during the postoperative period.

CONCLUSIONS AND CLINICAL RELEVANCE

Alterations in energy expenditure, protein synthesis, urinary nitrogen loss, and carbohydrate flux were evident in dogs with OSA, similar to results documented in humans with neoplasia. Changes were documented in REE as well as protein and carbohydrate metabolism in dogs with OSA. These changes were evident even in dogs that did not have clinical signs of cachexia.

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.

Direct effect of branched-chain amino acids on the growth and metabolism of cultured human hepatocellular carcinoma cells

Little is known about the influence of amino acid imbalance by supplementation of branched-chain amino acids (BCAAs) on human hepatocellular carcinoma (HCC). We investigated the effect of various BCAA concentrations in culture medium on the growth and metabolism of two human HCC cell lines: Hep G2 and KYN-1. DNA and protein syntheses were studied by radiolabeled thymidine and leucine uptake, Amino acid concentrations in cell and medium were measured with an amino acid analyzer. Expression and excretion of transforming growth factor (TGF)-alpha and TGF-beta1 were studied by immunostaining and enzyme linked immunosorbent assay methods. The cell growth was suppressed in media with higher and lower BCAA concentrations than Dulbecco's modified Eagle's medium, and this was grossly correlated with the incorporation of [3H]thymidine into DNA and incorporation of [3H]leucine into intracellular protein. Pretreatment with 10,000 nmol/ml of BCAA did not suppress the cell growth in subsequent culture in the standard Dulbecco's modified Eagle's medium, indicating that the effect of BCAAs was not cytocidal but cytostatic and reversible. BCAA and aromatic amino acid concentrations in cells increased in parallel as the BCAA level in medium was increased, despite the fixed aromatic amino acid level. Intracellular expression and extracellular excretion of TGF-alpha were higher at BCAA concentrations of 100 and 1,000 nmol/ml than at 10 or 1,000 nmol/ml. The present finding that the in vitro growth of HCC can be suppressed by enriched BCAA levels in medium may indicate that amino acid-imbalanced therapy with enriched BCAAs is useful in the treatment of HCC.

Negative impact of cancer chemotherapy on protein metabolism in healthy and tumor-bearing rats

Although chemotherapeutic agents are widely used in the treatment of cancer, few experimental data are available on their effects on host N metabolism. We studied the effects of a single intraperitoneal (IP) injection of cyclophosphamide ([CYP] 120 mg/kg), 5-fluorouracil ([5-FU], 50 mg/kg), cisplatinum ([CDDP], 5 mg/kg), or methotrexate ([MTX], 30 mg/kg). N balance was studied for 6 days following chemotherapy in healthy rats (n = 40) and in rats bearing Morris Hepatoma 7777 ([MH7777] n = 40) in a situation comparable to that of human cancer (tumor burden < 0.2% of body weight, moderate anorexia, and weight loss). In healthy rats, all drugs induced transient body weight loss, anorexia, and poor N balance. At day 6 posttreatment, all animals had resumed normal feed intake and positive N balance except CDDP-treated rats, which showed continued weight loss and poor N balance. CDDP and MTX exhibited antitumor activity; however, CDDP induced diarrhea in six of eight tumor-bearing rats. Drug-induced anorexia was more severe in tumor-bearing than in healthy treated rats. N balance was more severely decreased in MH7777-bearing rats than in healthy treated animals in response to 5-FU (159 +/- 36 v 273 +/- 27 mg N/2 d) and MTX (-66 +/- 36 v 153 +/- 37 mg N/2 d) at days 3 to 4 postinjection. These results establish the presence of drug-specific effects on host N balance and the existence of a drug-tumor interaction for N metabolism in the tumor-bearing host.

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.

Muscle performance and adenine-nucleotides status in MCA-sarcoma tumor-bearing rats

The reduction in DNA, RNA, amino acid, and total protein in muscle tissue of tumor-bearing rats may influence muscle function. The effects of MCA-sarcoma tumor burden on muscle performance and adenine nucleotides was evaluated in three fiber types of skeletal muscle. Twenty-one days after MCA-sarcoma tumor inoculation, the gastrocnemius-soleus muscle group of Fischer 344 rats was stimulated using an in situ preparation; tetanic stimulation for 10 min at 7.5, 15, or 30 tetani per min (TPM) or 60 TPM for 5 min (n = 6 control and six tumor-bearing rats/group). ATP, ADP, AMP, IMP, phosphocreatine, and creatine content in white and red gastrocnemius muscle and soleus muscle was measured. There were no differences among controls and tumor-bearing rats in force output; however, ATP content in the soleus muscle of tumor-bearing rats was significantly reduced after 30 TPM for 10 min or 60 TPM for 5 min. The performance of skeletal muscle, over a wide range of stimulation frequency, in tumor-bearing rats does not appear to be influenced by changes in adenine nucleotide content.

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.

Tumor and host response to arginine and branched chain amino acid-enriched total parenteral nutrition. A study involving Walker 256 carcinosarcoma-bearing rats

The metabolic effects of total parenteral nutrition (TPN) solutions containing different profiles of individual amino acids were investigated in the rats bearing Walker 256 carcinosarcoma. The rats were subcutaneously inoculated with 10(7) tumor cells and 6 days later were continuously infused intravenously for 8 days with three different TPN solutions. The experimental and control solutions were composed of high concentrations of branched chain amino acids (BCAA) and arginine (high Arg + BCAA TPN), high concentrations of BCAA (high BCAA TPN) and regular amino acids (regular TPN), respectively, and were isonitrogenous, isocaloric, and isovolemic. Rats receiving subcutaneous injection of saline rather than tumor cells received high Arg + BCAA TPN as pair-fed controls. The flooding dose method of 14C-leucine was used for the analysis of protein synthesis. With the feeding of high Arg + BCAA TPN, the tumor-bearing rats revealed a smaller increase of tumor volume and lower tumor fractional rates of growth (Kg) and synthesis (Ks) as well as protein synthesis (PS), compared with the high BCAA TPN and regular TPN in tumor-bearing rats. There were no significant differences of Ks and PS in liver and muscle between TPN groups, whereas tumor-bearing rats infused with high Arg + BCAA TPN displayed higher levels of whole-body Ks and PS than other TPN groups in tumor-bearing rats and pair-fed nontumorous rats. Except for liver RNA content which showed a lower level in tumor-bearing rats with high Arg + BCAA TPN, no other differences of DNA and RNA contents were found in tumor, liver, and muscle of the different TPN groups. The current results indicate that individual amino acids can influence tumor growth and protein metabolism, and that arginine, in combination with BCAA, may reduce tumor growth through a reduction in protein synthesis.

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.

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.

Branched chain amino acids as the protein component of parenteral nutrition in cancer cachexia

A prospective randomized trial was conducted to determine the effects of branched chain amino acids (BCAA) as the protein component of total parenteral nutrition (TPN) on protein kinetics in patients with intraabdominal adenocarcinoma. Nine malnourished patients were given both conventional TPN containing 19 per cent BCAA (AA) and isocaloric, isonitrogenous TPN containing 50 per cent BCAA (BCAA-TPN), in random order. Both [13C]leucine and [14C]tyrosine were employed as tracers to avoid the potential bias due to the different amino acid composition of the two TPN solutions. With BCAA-TPN, leucine and tyrosine flux increased significantly from (mean +/- s.d.) 158.0 +/- 37.2 to 243.5 +/- 75.8 mumol kg-1 h-1 (P less than 0.025) and from 35.0 +/- 8.4 to 42.6 +/- 11.0 mumol kg-1 h-1 (P less than 0.05) respectively. Leucine oxidation was significantly higher on BCAA-TPN (24.1 +/- 6.3 on AA versus 68.3 +/- 37.1 mumol kg-1 h-1, P less than 0.025) while tyrosine oxidation was significantly lower (3.7 +/- 1.8 mumol kg-1 h-1 on AA versus 2.5 +/- 2.0 mumol kg-1 h-1 on BCAA-TPN, P less than 0.05). Whole body protein synthesis and breakdown was significantly higher on BCAA-TPN by the tyrosine tracer (31.3 +/- 7.3 on AA versus 40.1 +/- 9.3 mumol kg-1 h-1, P less than 0.025 and 33.0 +/- 8.4 on AA versus 41.3 +/- 11.1 mumol kg-1 h-1, P less than 0.05) respectively. Using the leucine tracers both synthesis and breakdown were increased, but not significantly, from 133.8 +/- 40.0 to 175.3 +/- 65.1 mumol kg-1 h-1 and from 127.9 +/- 33.6 to 167.7 +/- 71.2 mumol kg-1 h-1 respectively. The fractional albumin synthetic rate increased significantly on BCAA-TPN from 4.3 +/- 2.9 on AA to 8.0 +/- 5.1 per cent per day (P less than 0.05). The reduction in tyrosine oxidation, suggesting improved protein utilization, coupled with an increase in protein and albumin synthesis, strongly support a positive benefit from BCAA-TPN in cancer cachexia.

Short-term effects of fat emulsion on serum lipids in postoperative patients

The effect of short-term infusion of intravenous fat on serum lipids was assessed in 23 patients who had elective cancer operations and were given 20% Intralipid for 5 days postoperatively as part of a standard total parenteral nutrition regimen. Serum lipids were measured prior to, during and after the 5-day infusion period. The percentage of cholesterol as high-density lipoproteins (HDL) fell from a mean preinfusion value of 34.7 +/- 2.8 to 27.9 +/- 2.5 (p less than 0.05), while the percentage of cholesterol as low-density lipoproteins (LDL) increased from 40.7 +/- 2.2 to 46.8 +/- 3.4 (p less than 0.05). Serum triglycerides fell significantly (p less than 0.01) from 106.2 +/- 13.7 mg/dl to 64.6 +/- 8.8 mg/dl at 3 days, being 85.3 +/- 3.7 mg/dl at 5 days. No significant change in percent cholesterol as very low-density lipoproteins (VLDL), or levels of serum total cholesterol or phospholipids occurred. Lipoprotein X was detectable in six patients after 5 days. To study triglyceride clearance 1.7 g/kg of fat emulsion was infused over 8 hr and serial blood samples obtained. Within 3 hr of stopping the fat infusion, triglyceride levels had fallen to preinfusion values.

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

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