Effects of Short-Term Creatine Supplementation on Whole-Body Protein Metabolism

Abstract

Creatine-monohydrate (CrM) supplementation has been shown to increase body mass and fat-free mass (FFM), however, the mechanism by which CrM affects body composition has not been determined. We investigated the effects of short-term CrM supplementation on whole-body protein turnover in 27 recreationally active male and female volunteers. Subjects underwent measurements prior to and following 9-10 days of CrM (20 g/d x 5 d, 5 g/d x 4-5 d) (n =14), or placebo (PL) (n =13) supplementation. Protein turnover was assessed using L-[1-¹³C] leucine stable isotope tracer, urinary urea nitrogen (N) excretion, and N-balance (Nbal) techniques. Total body mass (TBM), leucine flux, leucine oxidation, non-oxidative leucine disposal (NOLD), 24-hr urinary urea N excretion, and Nbal were determined before and after treatment. Additionally, the effects of CrM supplementation on renal function and metabolite clearance were evaluated by measuring creatinine (CTN) excretion, plasma CTN concentration, and CTN clearance. There was no effect for CrM as compared to PL on TBM, leucine flux, leucine oxidation, or NOLD. However, leucine oxidation was lower for the CrM-treated males as compared to the PL-treated males following supplementation (P < 0.05). Leucine flux and NOLD were higher for the males vs. the females (P < 0.05). Neither urinary urea N excretion nor Nbal were affected by treatment. Plasma [CTN], CTN excretion, and CTN clearance were also unchanged for CrM vs. PL. These findings suggested that CrM supplementation may have an effect upon leucine oxidation in males, yet there were no effects seen in females, nor were other indices of leucine turnover altered by CrM supplementation. Furthermore, short-term CrM supplementation did not have any adverse effects on renal function.