SHORT COMMUNICATION

Tumor Necrosis Factor a in Various Tissues of Insulin-Resistant Obese Koletsky Rats: Relations to Insulin Receptor Characteristics

J. HŘEBÍČEK, M. RYPKA, Z. CHMELA, J. VESELÝ, M. KANTOROVÁ, V. GOLDA

Institute of Pathological Physiology, Medical Faculty, Palacký University, Olomouc, and 1Institute of Experimental Neurosurgery, Faculty of Medicine, Charles University, Hradec Králové, Czech Republic

Received April 7, 1998
Accepted October 1, 1998

Summary
Tumor necrosis factor a (TNFa) was found to be significantly increased in skeletal muscles and retroperitoneal fat of obese insulin-resistant Koletsky rats as compared to control Wistar rats. This increase was accompanied by a depression of insulin receptor protein tyrosine kinase (PTK) activity. Neither the insulin-binding capacity nor insulin receptor affinity were related to this TNFa increase in these tissues. In the liver, no significant changes of TNFa content and only a lowering of insulin-binding capacity were found. It is concluded that an increased TNFa content in muscles and fat (but not in the liver) contributes to insulin resistance by lowering insulin receptor protein tyrosine kinase activity, while other insulin receptor characteristics (insulin-binding capacity and affinity of insulin receptors to the hormone) do not seem to be influenced by this factor.

Key words
Tumor necrosis factor a – Insulin resistance – Insulin receptor protein tyrosine kinase activity