ANABOLIC EFFECTS OF IGF-I COINFUSED WITH TOTAL PARENTERAL-NUTRITION IN DEXAMETHASONE-TREATED RATS

We determined the anabolic effects of recombinant human insulin-like g rowth factor I (rhIGF-I, 800 mu g/day) coinfused with total parenteral nutrition (TPN) in male Sprague-Dawley rats (230-250 g), with and wit hout dexamethasone (Dex, 70 mu g/day)-induced catabolism for 6 days. D ex without IGF-I increased serum insulin concentrations 300% and gluco se concentrations 20%; IGF-I plus Dex significantly reduced serum insu lin and glucose concentrations to TPN control levels. Animals given De x without IGF-I lost 30 +/- 3 g; IGF-I plus Dex reduced the weight los s to 9 +/- 3 g, P < 0.001. IGF-I without Dex resulted in a weight gain of 14 +/- 2 g compared with a gain of 4 +/- 1 g in TPN controls, P < 0.01. Determination of nitrogen balance and body composition confirmed that changes in body weight were due to corresponding changes in nitr ogen excretion and total body protein content. IGF-I significantly red uced TPN-induced intestinal atrophy, resulting in a 30% increase in we ight of the small intestine plus colon compared with TPN without IGF-I . These results indicate that coinfusion of rhIGF-I with TPN counterac ts Dex-induced insulin resistance and has a significant net anabolic e ffect when given with or without Dex in rats.