Anabolic effect of IGF-I coinfused with total parenteral nutrition in dexamethasone-treated rats

We determined the anabolic effects of recombinant human insulin-like growth factor I (rhIGF-I, 800 micrograms/day) coinfused with total parenteral nutrition (TPN) in male Sprague-Dawley rats (230-250 g), with and without dexamethasone (Dex, 70 micrograms/day)-induced catabolism for 6 days. Dex without IGF-I increased serum insulin concentrations 300% and glucose concentrations 20%; IGF-I plus Dex significantly reduced serum insulin and glucose concentrations to TPN control levels. Animals given Dex without IGF-I lost 30 +/- 3 g; IGF-I plus Dex reduced the weight loss 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 nitrogen excretion and total body protein content. IGF-I significantly reduced TPN-induced intestinal atrophy, resulting in a 30% increase in weight of the small intestine plus colon compared with TPN without IGF-I. These results indicate that coinfusion of rhIGF-I with TPN counteracts Dex-induced insulin resistance and has a significant net anabolic effect when given with or without Dex in rats.