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Nutrient Metabolism

Hypoenergetic High-Carbohydrate or High-Fat Parenteral Nutrition Induces a Similar Metabolic Response with Differential Effects on Hepatic IGF-I mRNA in Dexamethasone-Treated Rats¹

Karen R. Kritsch, Sangita Murali, Martin L. Adamo^*, Murray K. Clayton and Denise M. Ney²

Department of Nutritional Sciences, University of Wisconsin-Madison, WI 53706; ^* Department of Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229; and Departments of Statistics and Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706

²To whom correspondence should be addressed. E-mail: ney{at}nutrisci.wisc.edu.

The optimal level of energy for critically ill patients who require parenteral nutrition (PN) is unclear. Our objective was to determine whether 50% energy (50%E) restriction due to a reduction in carbohydrate or fat, with provision of adequate protein and micronutrients, ameliorates the detrimental effects of dexamethasone (Dex) on body protein catabolism, insulin resistance, and insulin-like growth factor-I (IGF-I) responses in rats administered PN. The experiment included 6 PN groups, adequate energy (AE) ± Dex, 50% AE with high carbohydrate (50%ECHO) ± Dex and 50% AE with high fat (50%EFAT) ± Dex. There was a significant interaction between energy level and Dex such that the increase in body catabolism due to 50%E from CHO or FAT was reduced by 50%, although the amount of body weight and nitrogen lost over 7 d was significantly greater with 50%E than with AE. AE+Dex induced a 60% increase in liver mass, whereas 50%E+Dex reduced the increase to 26%. AE+Dex induced a 5-fold increase in serum insulin level, whereas 50%E+Dex normalized the insulin to glucose ratio. Serum IGF-I levels were reduced 14–18% by Dex and 30% by 50%E. Hepatic immunoreactive IGF-I was significantly correlated with serum IGF-I and nitrogen balance. 50%ECHO and 50%EFAT had differential effects on hepatic IGF-I mRNA with a 40% decrease in IGF-I mRNA due to 50%EFAT+Dex. In summary, CHO or FAT hypoenergetic PN with adequate protein had similar effects in normalizing hyperinsulinemia, attenuating hepatomegaly, and reducing the increment, but not the total amount of body protein catabolism, induced by glucocorticoid excess.

KEY WORDS: • glucocorticoids • insulin • nitrogen catabolism • insulin-like growth factor-I