INTERACTIONS OF NORADRENALIN AND TUMOUR NECROSIS FACTOR α, INTERLEUKIN 4 AND INTERLEUKIN 6 IN THE CONTROL OF LIPOLYSIS FROM ADIPOCYTES AROUND LYMPH NODES

Abstract

The contributions of inflammatory and immunosuppressive cytokines and noradrenalin to the control of lipolysis in adipocytes surrounding and remote from lymph nodes were investigated in healthy adult guinea-pigs. A few hours after excision from fasting animals, spontaneous lipolysis in adipocytes from around the popliteal and mesenteric lymph nodes and omental “milky spots” was significantly lower than in those from elsewhere in the same depots, and much lower than in perirenal, epididymal or parametrial adipocytes. The perinodal adipocytes were consistently more sensitive to noradrenalin at 10−8, 10−7and 10−5M, and their maximum rate of lipolysis was higher. They also responded more strongly to pre-incubation for 24h with tumour necrosis factor α interleukin 6 and interleukin 4 than those elsewhere in the same depots. Tumour necrosis factor α and interleukin 6 applied alone stimulated lipolysis, but combined with interleukin 4, they suppressed glycerol release, especially in perinodal adipocytes, thereby creating large within-depot differences. These cytokines had minimal effects on lipolysis in perirenal or gonadal adipocytes.The authors conclude that adipocytes surrounding lymph nodes contribute little to whole-body energy supply during fasting, but are more sensitive than all others to cytokines and to noradrenalin, having higher maximum but lower minimum rates of lipolysis. These properties equip perinodal adipocytes for local interactions with lymphoid tissue.