Effect of energy repletion on dynamic aspects of protein metabolism of malnourished adolescent and young adult patients with cystic fibrosis during the first 12 days of treatment.

The short-term effect of nutritional rehabilitation on whole body protein metabolism of six malnourished (energy depleted) adolescent and young adult cystic fibrosis (CF) patients was examined during the first 12 days of treatment. Refeeding was accomplished using continuous nasogastric administration of an elemental diet. Intakes were 1.65 SD 0.3 g protein/kg/day and 85.3 SD 19.2 kcal/kg/day. Turnover measurements were carried out on four occasions, during the control period on a normal diet and days 4, 8, and 12 on the elemental diet. In response to refeeding, whole body amino nitrogen flux (Q) fell consistently over the study (p less than 0.05). Protein synthesis (S) and breakdown (B) also fell but their values did not reach statistical significance. On the other hand, there was a prompt increase in ratios S/Q and B/Q in response to tube feeding discernible on days 4 and 8 (p less than 0.05), but which returned to baseline by day 12. We conclude that malnourished CF patients who are still eating well have increased rates of protein turnover. There is a prompt response of protein metabolism to energy repletion with a progressive decline in rates during the first 12 days of treatment.