Metabolic alterations in liver, skeletal muscle, and fat tissue in response to different tumor burdens in growing sarcoma-bearing rats

Abstract

Metabolic alterations in growing sarcoma-bearing rats were studied and are presented in relationship to a small and moderate tumor burden (5 and 10% dry tumor weight of dry carcass weight). Sarcoma-bearing rats with a small tumor burden had decreased plasma concentration of glucose, significantly changed hepatic protein metabolism, increased lipolysis in fat tissue, but not significantly changed protein metabolism in skeletal muscles. Tumor-bearing rats with a moderate tumor burden had altered hepatic protein metabolism and plasma glucose in a manner similar to rats with a small tumor and similar to that previously reported for nongrowing sarcoma-bearing mice with a large tumor. This was also similar to findings in cancer patients. (K. Lundholm, S. Edström, I. Karlberg, L. Ekman, and T. Scherstén, Cancer Res. 40: 2516–2522, 1980; K. Lundholm, S. Edström, L. Ekman, I. Karlberg, A-C. Bylund, and T. Scherstén, Cancer 42, 453–461, 1978). In contrast to sarcomabearing mice and man, these rats with a “moderate tumor” still had unchanged nitrogen balance in skeletal muscle. We conclude that metabolic alterations in the liver precede catabolic reactions in peripheral tissues and that initiating factors for increased lipolysis are earlier than those factors initiating wasting of skeletal muscles in growing sarcoma-bearing rats.