The purpose of the present study was to determine whether acute changes in the insulin-like growth factor (IGF) system induced by mild surgical trauma/fasting or endotoxin [lipopolysaccharide (LPS)] are differentially modulated by total enteral nutrition (TEN) or total parenteral nutrition (TPN). Rats had vascular catheters and a gastrostomy tube surgically placed and were fasted overnight. The next morning animals randomly received an isocaloric, isonitrogenous (250 kcal · kg-1 · day-1, 1.6 g N · kg-1 · day-1) infusion of either TEN or TPN for 48 h. Then rats were injected intravenously with Escherichia coli LPS (1 mg/kg) while nutritional support was continued. Time-matched control animals were injected with saline. After mild surgical trauma and an 18-h fast, TEN was more effective at increasing plasma IGF-I levels than TPN. Subsequent injection of LPS decreased IGF-I in blood, liver, and muscle in both TEN- and TPN-fed rats compared with saline- injected control animals. However, this decrease was ~30% greater in rats fed TPN compared with those fed TEN. LPS-induced downregulation of IGF-I mRNA expression in liver and muscle was also more prominent in TPN-fed rats. The LPS-induced increase in plasma corticosterone and tumor necrosis factor-α was greater (2- and 1.6-fold, respectively) in TPN-fed rats, and these changes were consistent with the greater reduction in IGF-I seen in these animals. In similarly treated rats allowed to survive for 24 h after LPS injection, the LPS-induced increase in the urinary 3-methylhistidine-to- creatinine ratio was smaller in TEN-fed rats. In summary, LPS reduced systemic levels of IGF-I as well as IGF-I protein and mRNA in critical target organs. Enteral feeding greatly attenuated this response. Maintenance of higher IGF-I levels in TEN-fed rats was associated with a reduction in inflammatory cytokine levels and lower rates of myofibrillar degradation.
|Original language||English (US)|
|Journal||American Journal of Physiology - Endocrinology and Metabolism|
|Issue number||3 39-3|
|State||Published - Mar 1999|
All Science Journal Classification (ASJC) codes
- Endocrinology, Diabetes and Metabolism
- Physiology (medical)