Optimal Protein Load in Children with Cystic Fibrosis

1. Optimal Protein Load in Children with Cystic Fibrosis WKZ V.G.M.Geukers1, J.H.Oudshoorn2, J.A.J.M.Taminiau1, C.K. van der Ent2, P.P.M.Schilte3, A.F.C.Ruiter4, M.T.Ackermans4, E.Endert4, C.F.Jonkers-Schuitema4, H.S.A.Heymans1, H.P.Sauerwein4 Depts. of Pediatrics of Emma Children’s Hospital, Amsterdam1, Wilhelmina Children’s Hospital, Utrecht2 and Medical Center Alkmaar3; Dept. of Endocrinology and Metabolism, Academic Medical Center Amsterdam4, The Netherlands Introduction Results Worldwide pediatric CF-patients are advised to consume 3 g/kg/day of dietary protein, in comparison with 1,5 g/kg/day in healthy children. The ratio behind this advise is the indigestion and malabsorption of nutrients in CF, combined with increased resting energy expenditure (REE) due to recurrent infections and continuous catabolism, in which protein breakdown is predominant. Since this catabolism is difficult to influence exogenously, efforts are made to increase protein synthesis by increasing dietary protein intake and thus enhance net nitrogen retention. However, if the intake of protein is too high, this leads to an increase of (energy demanding) protein oxidation and urea production. Protein synthesis in valine data increased 1.3-fold in HP diet, without change of endogenous protein catabolism: * Purposeand hypothesis Increase protein synthesis: MP vs LP 1.15-fold (p=0,0012), HP vs MP 1.14-fold (p=0,0004), HP vs LP 1.31-fold (p<0.0001). No significant overall change of endogenous Ra-valine (p=0,16) To determine optimal protein load (per kg bodyweight) in ambulant children with CF, defined as maximal protein synthesis. It was expected that endogenous protein catabolism is not altered by increasing dietary protein load. Protein synthesis in urea data increased 5.2-fold in HP diet, despite increased urea production: Methods 8 CF patients, aged 7 to 12 years, received 3 isocaloric diets with different amounts of protein (1,5 vs. 3 and 5 g/kg/day; LP, MP and HP resp.) in random order. The diets were givenvia continuous gastric tube feeding for 4 days with a 6 weeks interval. At day 4 data were obtained during a steady state of stable isotope (13C-valine and 15N-urea) infusion. Dietary effects on protein synthesis were studied by two independent indicators: non-oxidative disposal of valine and net nitrogen retention in the body. Repeated measurement analysis of variance (SAS) was used to establish significancy. The rate of appearance of urea increased significantly with higher protein load (MP vs LP p=0,01, HP vs MP p=0,0002, HP vs LP p<0.001). Still, retention of nitrogen (=protein synthesis) increased significantly in MP vs LP (p=0,009), HP vs MP (p=0,05) and even 5.2 fold in HP vs LP (p<0.0001). Study design Summary 8.25 am 9.30 11.00 12.30 1.00 1.30 2.00/2.10/2.20/2.30 pm ↑ ↑ ↑ ↑ ↑ ↑ ↑↑↑↑ blood samples indirect calorimetry (2.00-2.30 pm) ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ breath samples ↑ priming with isotope valine, urea and sodium carbonate 8.30 am 2.30 pm isotope infusion of valine and urea With increasing protein load from 1,5 to 5 g/kg/day, protein synthesis (both non-oxidative disposal of valine and net retention of nitrogen) increased significantly, without significant alterations in protein breakdown. Both the valine and urea data suggested that in this study the optimal protein load in children with cystic fibrosis is 5 g/kg/day. Conclusions • Protein synthesis in children with CF is further increased by a dietary protein load of 5 g/kg/day. • Urea production is also maximal at HP-diet, but this diet still results in the highest net retention of nitrogen. • Endogenous protein catabolism is not influenced by dietary protein load.