No effect of creatine supplementation on human myofibrillar and sarcoplasmic protein synthesis after resistance exercise

Abstract

. No effect of creatine supplementation on human myofibrillar and sarcoplasmic protein synthesis after resistance exercise. Am J Physiol Endocrinol Metab 285: E1089-E1094, 2003. First published June 24, 2003 10.1152/ajpendo.00195.2003.-Muscle hypertrophy during resistance training is reportedly increased by creatine supplementation. Having previously failed to find an anabolic effect on muscle protein turnover at rest, either fed or fasted, we have now examined the possibility of a stimulatory effect of creatine in conjunction with acute resistance exercise. Seven healthy men (body mass index, 23 Ϯ 2 kg/m 2 , 21 Ϯ 1 yr, means Ϯ SE) performed 20 ϫ 10 repetitions of leg extension-flexion at 75% one-repetition maximum in one leg, on two occasions, 4 wk apart, before and after ingesting 21 g/day creatine for 5 days. The subjects ate ϳ21 g maltodextrin ϩ 6 g protein/h for 3 h postexercise. We measured incorporation of [1-13 C]leucine into quadriceps muscle proteins in the rested and exercised legs. Leg protein breakdown (as dilution of [ 2 H5]phenylalanine) was also assessed in the exercised and rested leg postexercise. Creatine supplementation increased muscle total creatine by ϳ21% (P Ͻ 0.01). Exercise increased the synthetic rates of myofibrillar and sarcoplasmic proteins by two-to threefold (P Ͻ 0.05), and leg phenylalanine balance became more positive, but creatine was without any anabolic effect. skeletal muscle; protein turnover THE USE OF CREATINE SUPPLEMENTATION as an ergogenic aid has increased markedly, especially among athletes requiring high power outputs during so-called explosive events. In investigating the possible mechanisms for the claimed improvements in performance, many workers have reported that creatine supplementation is accompanied by a significant increase in lean body mass (1,2,4,9,14). There is evidence that the increase in muscle mass does not simply represent an increase in total body water but is mainly intracellular, suggesting that the body cell dry mass has increased (10). Also, there are a number of reports showing increases in muscle fiber area as a result of consuming creatine while training using resistance exercise (29, 30) or during treatment of patients with muscle atrophy (13, 28).The mechanism of the creatine-associated effect on muscle mass is unknown. If it is the result of a direct effect of creatine, it should stimulate muscle protein synthesis or decrease muscle protein breakdown. Increased creatine availability has been reported in studies of animal skeletal and cardiac muscle in vitro to stimulate protein synthesis (15,16,33), although other investigators (11) were unable to confirm this.In starting to investigate the possible effects on human muscle, we began by studying the effect of creatine supplementation on human muscle protein turnover at rest in the fasted and fed conditions (20). In that study, we measured myofibrillar protein synthesis and leg protein breakdown in healthy young men before and after 5 days of dietary creatine supplementation sufficient to r...

Myofibrillar and collagen protein synthesis in human skeletal muscle in young men after maximal shortening and lengthening contractions

“…In this report, we present values for resting and postexercise myofibrillar (15) and collagen protein synthesis (1) similar to those we have reported previously. As expected, resistance exercise in conjunction with postexercise feeding significantly elevated myofibrillar protein synthesis above rest in both conditions (20).…”

“…Whereas the extent of the reduction in the rate of protein synthesis within perfused rat skeletal muscle during maximal contractions is correlated with falls in phosphocreatine and the ATP:ADP ratio (indexes of intense muscle activity) (4), it is unclear whether myofibrillar protein synthesis in human skeletal muscle would be influenced by the greater exercise intensity during SC at 4.5 h in the present investigation. Louis et al (15) recently found that creatine supplementation, which should maintain the PCr:Cr ratio during intense exercise (13) and possibly attenuate an exercise-induced fall in the ATP-to-ADP ratio, had no effect on myofibrillar protein synthesis 3 h after an acute bout of exercise. The authors speculated that the change in protein synthesis after exercise was in part dependent on the extent of the reduction in the energy status of the muscle during exercise (15).…”

“…Louis et al (15) recently found that creatine supplementation, which should maintain the PCr:Cr ratio during intense exercise (13) and possibly attenuate an exercise-induced fall in the ATP-to-ADP ratio, had no effect on myofibrillar protein synthesis 3 h after an acute bout of exercise. The authors speculated that the change in protein synthesis after exercise was in part dependent on the extent of the reduction in the energy status of the muscle during exercise (15). If this were true, we could expect to find a greater myofibrillar protein synthesis after maximal SC compared with LC, which was not the case.…”

Decrease in Akt/PKB signalling in human skeletal muscle by resistance exercise

“…As suggested in Fig. 4, this priming of p70 s6k possibly participates in the potentiation of protein synthesis in exercised muscles when nutrients are provided during recovery (Louis et al 2003). Indeed, nutrients are required to achieve a positive protein balance following exercise at least in part by initiating signalling leading to the phosphorylation of Thr 389 (Cuthbertson et al 2006) and therefore conferring full activation of p70 s6k .…”

Heat shock response and autophagy—cooperation and control

“…In response to acute resistance exercise, there was a significant increase in mixed protein synthesis in untrained subjects but not in the trained athletes: 113 however, the myofibrillar protein synthesis rate was elevated in both untrained and trained subjects in response to resistance exercise. 114,115 The effect of the training protocol and muscle protein synthesis is documented in exercise literature as well. Both resistance [116][117][118] and endurance 119 exercise training result in a marked increase in skeletal muscle protein synthesis rate.…”