Effect of beta-alanine and carnosine supplementation on muscle contractility in mice


Journal Title (Medline/Pubmed accepted abbreviation): Med. Sci. Sports Exerc.
Year: 2013
Volume: 45
Issue: 1
Page Numbers: 43-51
doi: 10.1249/MSS.0b013e31826cdb68

Summary of background and research design:
Background: β-Alanine is an amino acid that is part of the molecule carnosine in skeletal muscle. Long term supplementation with β-alanine has been shown to improve performance during high intensity exercise such as sprinting.
In skeletal muscle in mice (but not humans), β-alanine makes up both carnosine and anserine, another related histidine-containing dipeptide.

Hypothesis: Supplementation with carnosine and β- alanine will increase the concentrations of carnosine and anserine in mouse muscle, though may decrease the content of taurine. Also, carnosine and β-alanine supplementation will increase exercise-related function such as increasing power and decreasing fatigue.

Experimental Design: block randomized based on baseline body mass, double-blind, placebo-controlled

Subjects: A total of 66 mice

Treatments: The mice were fed with a standard chow diet with one of 6 beverages:
1. water (control)
2. water with 0.1% carnosine
3. water with 0.5% carnosine
4. water with 1.8% carnosine
5. water with 0.6% β-alanine
6. water with 1.2% β-alanine

Protocol: The mice were randomized to one of the 6 treatment groups. Initially, it was not known how much carnosine to add to the water to elicit effects, so 0.1% and 0.5% carnosine were provided for 12 weeks. There were no effects at these concentrations, so the dose was increased. Treatments 4-6 (above) were provided for 8 weeks. Twice a week, new bottles were provided and weight was recorded. At the completion of the study, soleus, tibialis anterior, and extensor digitorum longus (EDL) muscle were removed while the mouse was anesthetized. The mouse was then euthanized. The soleus and the EDL muscles were assessed for muscle contraction properties such as force, contraction speed, relaxation speed, and fatigability while stimulated by capacitor discharges. The three types of muscle were analyzed for concentration of carnosine, anserine, and taurine.

Summary of research findings:
  • Addition of β-alanine or carnosine to the drinking water led to a decrease in liquid consumption of up to 35%.
  • Those that consumed β-alanine gained slightly less weight than those in the carnosine and control groups, but the differences were not statistically significant.
  • Carnosine addition to water at 1.8% caused an increase in carnosine and anserine in the mice's EDL but not the tibialis anterior. Taurine levels did not decrease with supplementation.
  • Carnosine addition to water at 1.8% caused an increase in carnosine and anserine in the mice's EDL but not the tibialis anterior. Taurine levels did not decrease with supplementation.
  • Supplementation of the mice's water with 1.2% β-alanine, but not 0.6% β-alanine, increased carnosine content in the EDL and the tibialis anterior. Anserine content was also increased in both muscle types, though the increase was only statistically significant in the EDL. However, taurine concentrations in the tibialis anterior were 18% lower with 1.2% β-alanine in the water compared to the control mice.
  • Twitch and contractile properties were not different between control mice and mice supplemented with 1.8% carnosine or 1.2% β-alanine.
  • When assessing frequency-induced muscle contraction, 1.2% β-alanine led to a 10-32% greater force output in the soleus and the EDL. Carnosine supplementation did not influence force output.
  • Soleus muscle fibers from mice that were supplemented with 1.2% β-alanine were more resistant to fatigue, though not EDL fibers. Carnosine supplementation did not attenuate fatigue in either muscle.

Key practice applications: This study shows that chronic supplementation with either β-alanine or carnosine can increase carnosine content in the muscle (among other β-alanine-containing molecules in mice that are not relevant in humans). Furthermore, β-alanine supplementation led to a greater contractile response in the muscle fibers, as well as reduced fatigue in the soleus muscle.

Limitations:
  • The authors noted that increased supplement in the water led to decreased water consumption. It is unknown how possible dehydration could have influenced the results.
  • These results were obtained in mice, not humans, so caution is necessary for extrapolation of the findings to humans. However, these findings point to a new and potentially alternative method of action for the proposed ergogenic effects of beta-alanine supplementation. The usual explanation is the buffering capacity of increased muscle carnosine concentrations.
  • The mice were housed 3-4 per cage, so it was not possible to quantify the amount of supplement consumed by each individual mouse.
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