Metabolic effects of medium chain triglyceride-enriched total parenteral nutrition in rats bearing Yoshida sarcoma

The ability of medium chain triglyceride-enriched total parenteral nutrition to support host tissue in a model of cancer cachexia was assessed by measuring tumor growth, body weight, nitrogen balance, energy expenditure, leucine kinetics, fractional protein synthetic rate of tumor, liver, and abdominis rectus muscle, and plasma levels of glucose and albumin. Male Sprague-Dawley rats (85-90 gm) received 10(7) cells of viable Yoshida sarcoma subcutaneously on day 0. Control rats received injections of sterile saline. On day 10 rats underwent central venous cannulation and were randomized to one of three isocaloric diets. One group received amino acids and dextrose, while the other two groups were infused with amino acids, dextrose, and fat as either long chain triglyceride or a physical mixture of medium chain triglyceride: long chain triglyceride (3:1). On day 14 L-1-(14)C-leucine was added to the diet to study protein kinetics, and energy metabolism was measured by indirect calorimetry. Both tumor-bearing and nontumor-bearing rats demonstrated improved nitrogen balance when given medium chain triglyceride-enriched total parenteral nutrition. Tumor-bearing rats had reduced resting energy expenditure vs. nontumor-bearing, while rats receiving total parenteral nutrition without fat had significantly greater respiratory quotients. Tumor-bearing rats had lower total body weight vs. nontumor-bearing on day 10, but body weight of tumor-bearing and nontumor-bearing did not differ on day 14. Whole body protein breakdown decreased and leucine balance increased in tumor-bearing rats as compared to nontumor-bearing. Total liver mass was greater in tumor-bearing rats, but liver protein fractional protein synthetic rate decreased in tumor-bearing rats vs. nontumor-bearing. Tumor growth rate and fractional protein synthetic rate were not altered by the parenteral diet. The data confirm an altered metabolism in the tumor-bearing host, and suggest that medium chain triglyceride can better support host tissue.