Changes in muscle carnosine of subjects with 4 weeks supplementation with a controlled release formulation of beta‐alanine (Carnosyn™), and for 6 weeks post

Abstract

Muscle Carnosine (M‐Carn) synthesis is limited by the availability of ?‐Alanine ( ?‐Ala) but can be increased by supplementation with ?‐Ala. This is of interest to athletes since increased levels of muscle M‐Carn have previously been shown to improve exercise performance. Above 10mg/kg bwt, however, ?‐Ala in solution or rapidly‐dissolving capsules causes symptoms of paraesthesia, despite the amount being less than that available from normal meat ingestion.PURPOSETo investigate the change in M‐Carn in subjects supplemented with a controlled‐release ?‐Ala formulation.METHODSeven males received 2x800mg ?‐Ala controlled release tablets, 4/d for 4w. Controlled release tablets were Carnosyn(tm) supplied by Collegiate Sports Nutrition. A muscle biopsy from the vastus lateralis was taken at 0 and 4w, and 3 and 6w post supplementation. No control group was included as several previous studies have demonstrated no change in M‐Carn without ?‐Ala supplementation.RESULTSSubjects did not experience paraesthesia. Mean (±SD) M‐Carn at 0 and 4w, and, 3 and 6w post supplementation were 25.9±4.3, 41.3±5.5, 38.3±6.7 and 35.4±5.5 mmol.kg−1 dry muscle. Post supplementation M‐Carn declined via first‐order kinetics with a half‐life (t½) determined to be 8.6w.CONCLUSIONThe controlled release ?‐Ala formulation was effective in raising M‐Carn. Following supplementation, levels of M‐Carn declined slowly with a t½ ~9w.

Kinetics of Muscle Carnosine Decay after β-Alanine Supplementation: A 16-wk Washout Study

“…Moreover, we used an 8-wk, high-dose, supplementation protocol, providing a total accumulated β-alanine dose of ~360 g, which resulted in ~90% increase in M-Carn. Both the total accumulated dose and the carnosine accrual in our study were substantially greater than the doses (~90 to 180 g) and the increases in M-Carn (<40% to 60%) shown in previous studies (17)(18)(19). This might account, at least in part, for some of the differences between our results and those previously reported (17)(18)(19).…”

“…We also showed that carnosine washout can be described by a linear decay, although an exponential model can also describe the washout kinetics just as well as the linear model. The calculated t 1/2 for M-Carn was 4.6 (95% CI, 3.2-7.0) wk in the exponential decay model in our study, which is not too dissimilar to the 5.8 wk reported by Baguet et al (17) but somewhat shorter than the 8.6 wk reported by Harris et al (19). We also provided evidence for the association between M-Carn and high-intensity exercise performance after both supplementation and washout.…”

“…Because the catalytic efficiency of CN2 is poor and the rate of carnosine degradation is subsequently low, the increase in CN2 activity due to the increased substrate availability would be just sufficient to unbalance carnosine homeostasis toward degradation, but not sufficiently fast to result in an observable exponential curve that is clearly distinguishable from a linear curve. The notion that only minor differences between carnosine synthesis and degradation underpin the slow washout pattern, leading to a remarkable similarity between linear and exponential decays, can explain the inconsistencies between previous studies in describing the kinetics of carnosine decay (17)(18)(19). The proposed mechanisms underlying carnosine loading and washout are illustrated in Figure 5.…”

“…To date, only three studies have evaluated muscle carnosine washout (17)(18)(19), with conflicting data being reported. Harris et al (19) were the first to study carnosine washout; using chromatographic carnosine determination in muscle biopsy samples, they reported an exponential decay for carnosine with a half-life (t ½ ) of 8.6 wk after β-alanine supplementation (6.4 g•d −1 for 4 wk).…”

“…To date, only three studies have evaluated muscle carnosine washout (17)(18)(19), with conflicting data being reported. Harris et al (19) were the first to study carnosine washout; using chromatographic carnosine determination in muscle biopsy samples, they reported an exponential decay for carnosine with a half-life (t ½ ) of 8.6 wk after β-alanine supplementation (6.4 g•d −1 for 4 wk). Subsequently, Baguet et al (17) supplemented 4.8 g•d −1 of β-alanine for 5-6 wk, and using hydrogen magnetic resonance spectroscopy to quantify muscle carnosine, they reported linear (i.e., zero order) washout kinetics in M-Carn with a ~30% reduction in M-Carn occurring in the third week of washout; by the ninth week, mean carnosine had returned to presupplementation levels.…”