Kenji Kitazato

Effect of arginine-enriched total parenteral nutrition on the host-tumor interaction in cancer-bearing rats

By using a transplantable Yoshida sarcoma in a rat total parenteral nutrition model, we measured the effectiveness of an arginine-enriched amino acid solution (AI-82) in terms of leucine kinetics and nitrogen balance as indicators of host-tumor nutrition interaction compared with that of a conventional amino acid solution (Proteamin12). When tumor-bearing rats received isocaloric total parenteral nutrition solutions for 7 days, AI-82 significantly improved host nitrogen balance and significantly decreased the tumor-nitrogen trap throughout the experimental period. Leucine kinetics of whole body and tissues were also determined by a 4-hour continuous infusion of each total parenteral nutrition solution containing 14C-leucine. Significantly increased whole-body leucine oxidation (p < .01) without an increase in leucine release from normal tissues was observed in the AI-82 group. Total incorporation of 14C-leucine into whole muscle was significantly elevated (p < .05) without changes in muscle protein degradation in the AI-82 group. In the whole tumor, AI-82 tended to decrease total incorporation of 14C-leucine, but there was no difference in leucine release caused by protein breakdown between the two groups. These findings suggest that AI-82 can improve the nutritional status of the host over that of the tumor.

Gene expression analysis using human cancer xenografts to identify novel predictive marker genes for the efficacy of 5-fluorouracil-based drugs

The development of a diagnostic method for predicting the therapeutic efficacy or toxicity of anticancer drugs is a critical issue. We carried out a gene expression analysis to identify genes whose expression profiles were correlated with the sensitivity of 30 human tumor xenografts to 5‐fluorouracil (5‐FU)‐based drugs (tegafur + uracil [UFT], tegafur + gimeracil + oteracil [S‐1], 5′‐deoxy‐5‐fluorouridine [5′‐DFUR], and N4‐pentyloxycarbonyl‐5′‐deoxy‐5‐fluorocytidine [capecitabine]), as well as three other drugs (cisplatin [CDDP], irinotecan hydrochloride [CPT‐11], and paclitaxel) that have different modes of action. In the present study, we focused especially on the fluoropyrimidines. The efficacy of all anticancer drugs was assayed using human tumor xenografts in nude mice. The mRNA expression profile of each of these xenografts was analyzed using a Human Focus array. Correlation analysis between the gene expression profiles and the chemosensitivities of seven drugs identified 39 genes whose expression levels were correlated significantly with multidrug sensitivity, and we suggest that the angiogenic pathway plays a pivotal role in resistance to fluoropyrimidines. Furthermore, many genes showing specific correlations with each drug were also identified. Among the candidate genes associated with 5‐FU resistance, the dihydropyrimidine dehydrogenase mRNA expression profiles of the tumors showed a significant negative correlation with chemosensitivity to all of the 5‐FU based drugs except for S‐1. Therefore, the administration of S‐1 might be an effective strategy for the treatment of high dihydropyrimidine dehydrogenase‐expressing tumors. The results of the present study may enhance the prediction of tumor response to anticancer drugs and contribute to the development of tailor‐made chemotherapy. (Cancer Sci 2006; 97: 510 – 522)

Arginine-Enriched Solution Induces a Marked Increase in Muscle Glutamine Concentration and Enhances Muscle Protein Synthesis in Tumor-Bearing Rats

Using a transplantable Yoshida sarcoma in a rat model of total parenteral nutrition (TPN), we measured the effectiveness of an arginine-enriched amino acid solution (AI-82) on muscle glutamine concentration and muscle protein synthesis compared with that of a conventional amino acid solution (Proteamin12). After tumor-bearing rats had been given one of two isocaloric TPN regimens for 6 days, [15N]glycine (99 atom %) containing TPN solution was infused into animals at a constant rate of 8 mg of [15N]glycine per hour for 18 hours, after which the liver, skeletal muscle (gastrocnemius muscle), and tumor protein synthesis rates were measured. A significantly increased whole muscle protein synthesis rate was observed in the AI-82 group; there was no difference in the whole liver and tumor protein synthesis rates between the two groups. When each TPN solution was administered for 1 week, muscle concentrations of arginine, ornithine, glutamine, and glutamate were considerably higher in the AI-82 group than in the Proteamin12 group, and these differences were also accompanied by a decrease in the plasma branched-chain amino acid (BCAA) (leucine, isoleucine, and valine) levels in the AI-82 group. The high levels of muscle glutamine concentration in the AI-82 group were investigated in connection with the high use of exogenous branched-chain amino acids.

Alteration of energy substrates utilized by small and large thymocytes in resting and stimulating state

Abstract Glucose and glutamine are well known as a major energy source for proliferating rat thymocytes. Nevertheless, it is still unclear whether there is a difference in utilization of energy substrates between the mature and immature thymocytes. In the present study, we prepared small and large thymocytes from male Wistar rats by Percoll density-gradient centrifugation to answer these questions. The average diameter of the large thymocytes was approximately 1.6 times that of the small thymocytes. By flow cytometry analysis, the most of small thymocytes was immature T cells (CD4 + 8 + cells) and about 20% of the large thymocytes was CD4 + 8 − T cells. After phytohemagglutinin (PHA) and concanavalin A (ConA) stimulations in vitro , large thymocytes showed significantly higher incorporation of [ 3 H]thymidine. In contrast, small thymocytes did not exhibit a proliferative response at all. After 48 hours culture of large or small thymocytes with or without ConA stimulation, the alterations in the medium concentrations of glucose, pyruvate, lactate, ketone bodies, free fatty acids (FFA), and amino acids were analyzed. The resting large thymocytes showed significantly higher consumption of glucose and production of lactate, which were further elevated in response to ConA. In contrast, the resting small thymocytes showed slight consumption of glutamine and production of glucose. When small thymocytes were stimulated with ConA, a change to glucose consumption and lactate production was observed without an increase in either total substrate consumption or proliferative response. These results suggest that the substrates utilized by thymocytes vary from immature to mature cells and that these changes of energy substrates utilized by thymocytes are closely related to the maturation and function of thymic T lymphocytes.

The increase in muscle glutamine concentration in hindlimbs of tumor-bearing rats is associated with facilitation of arginine and ornithine uptake

Abstract Our previous study showed that the muscle glutamine concentration was markedly elevated by administration of an arginine-enriched amino acid solution (AI-82) as a total parenteral nutrition (TPN) regimen in Yoshida sarcoma-bearing (TB) rats (1). Here, by using the same TPN model, we determined the net uptake/release of amino acids and several carbohydrates from the hindlimbs of TB rats administered AI-82 by measurement of arteriovenous differences in order to estimate what kinds of amino acids and substrates were utilized for glutamine synthesis in the hindlimbs compared with rats administered conventional amino acid solution (Proteamin 12). AI-82 administration resulted in a marked enhancement of the uptakes of arginine (P