Effect of Insulin With Oral Nutrients on Whole-Body Protein Metabolism in Growing Pubertal Children With Type 1 Diabetes

Insulin treatment of children with insulin-dependent diabetes mellitus improves whole body protein balance. Our recent study, conducted in pubertal children with type I diabetes with provision of both insulin and amino acids, indicated a positive effect of insulin on protein balance, primarily through decreased protein degradation. The current study was undertaken to assess the effect of insulin on protein metabolism in adolescents with type I diabetes during oral provision of a complete diet. Whole-body protein metabolism in six pubertal children (13-17 y) with type I diabetes mellitus was assessed with L-[1-C-13] leucine during a basal (insulin-withdrawn) period and during infusion of 0.15 U/kg/h regular insulin with hourly meals to meet protein and energy requirements. Net leucine balance was significantly higher with insulin and nutrients (13.1 +/- 6.3 mu mol leucine/kg/h) than in the basal state (-21.4 +/- 2.8, p < 0.01) with protein degradation decreased from 138 +/- 5.6 mu mol leucine/kg/h to 108 +/- 5.9 (p < 0.01) and no significant change in protein synthesis. Even with an ample supply of nutrients, insulin does not increase whole-body protein synthesis in pubertal children with type I diabetes mellitus and positive protein balance is solely due to a substantial reduction in the rate at which protein is degraded. (Pediatr Res 65: 109-112, 2009)