The Effect of Oral Leucine on Protein Metabolism in Adolescents with Type 1 Diabetes Mellitus

Whole body protein catabolism results when the rate at which body protein is synthesized is less than the rate at which body protein is degraded. Insulin is among the many factors which regulate body protein metabolism. The lack of insulin associated with type 1 diabetes results in the loss of body protein, and insulin treatment reverses the loss of body protein resulting in increased lean body mass [1]. Several animal studies have demonstrated the importance of insulin in regulating the rate of protein synthesis particularly in muscle tissue (e.g., [2–7]). In contrast, studies of whole-body protein metabolism in adult humans with type 1 diabetes [8–13] and prepubertal children [14] have suggested that the primary effect of insulin is a reduction in the rate of protein degradation rather than a stimulation of the rate of protein synthesis. While provision of insulin to individuals with type 1 diabetes enhances the accretion of body protein mass, there are also data from adults [15] and adolescents females [16] suggesting that long-term insulin therapy also results in accumulation of body fat compared to nondiabetic individuals. The current study was undertaken to determine if the anabolic effect of insulin on protein metabolism could be enhanced by the concurrent provision of a diet enriched with the amino acid, leucine.In clinical studies, solutions of branched-chain amino acids have improved nitrogen balance in patients with surgical stress [17–19]. In patients with liver carcinoma, provision of branched-chain amino acids has been demonstrated to result in decreased morbidity and improved quality-of-life [20], reduced complications following surgery [21], and decreased length of hospital stay [22]. In healthy subjects, provision of essential amino acids in both young and old subjects results in a stimulation of the rate at which muscle protein is synthesized [23, 24]. In elderly subjects, enriching the essential amino acid supplement with additional leucine result