Vegetarianism, female gender and increasing age, but not CNDP1 genotype, are associated with reduced carnosine levels in humans


Journal Title (Medline/Pubmed accepted abbreviation): Amino Acids
Year: 2011
Volume: 40
Page numbers: 1221-1229
doi (if applicable): 10.1007/s00726-010-0749-2

Summary of Background and Research Design

Background: Carnosine (β-alanyl-L-histidine) is a dipeptide that is imperative to skeletal muscle function. In humans, muscle carnosine concentrations can vary by up to 4 times among individuals, and it has been shown that higher levels of carnosine improve physical performance by delaying fatigue. Beta-alanine is the rate-limiting amino acid for muscle carnosine synthesis.

Hypothesis:
  1. Because habitual consumption of meat, fish, or β-alanine supplements is associated with increased carnosine levels, vegetarians will have lower carnosine concentration than omnivores.
  2. As has been shown in previous studies, males will have more carnosine than females and carnosine levels will decrease with age.
  3. Testosterone levels will positively correlate with carnosine concentration.
  4. A polymorphism* on CNDP1 (a gene that encodes for carnosinase, which is responsible for breaking down carnosine) will cause carnosinase to last longer in the blood and therefore result in lower total blood carnosine concentrations.

*Polymorphism – small differences in genes from one person to another. If the variation is present in at least 1% of the population it is a “polymorphism”, otherwise the difference(s) is a “mutation”


Subjects: A total of 149 adults participated- 12 male vegetarians (for at least 8 yrs), 82 male omnivores, and 55 female omnivores. Not all subjects were assessed for all variables.

Experimental design: no intervention

Treatments and protocol: To measure muscle carnosine levels in the soleus, gastrocnemius, and tibialis anterior (3 leg muscles), proton magnetic resonance spectroscopy (1H-MRS) was employed. This is a noninvasive method, similar to MRI. Venous blood was collected to assess the concentration of testosterone, luteinizing hormone (LH), carnosinase activity, and CNDP1. To assess β-alanine intake, subjects filled out a questionnaire evaluating their consumption of meat and fish.

Summary of research findings
  • For men, carnosine levels were 28% higher in the gastrocnemius, 36% higher in the soleus, and 82% higher in the tibialis anterior compared to women.
  • Carnosinase activity was significantly higher in women that men (p<0.001).
  • Carnosine concentrations showed a decreasing trend with increasing age in people 19-47 yrs old.
  • Though testosterone was negatively correlated with age in males, it did not correlate with carnosine content.
  • In vegetarians, carnosine concentrations were 17% less in the soleus, 26% lower in the gastrocnemius, and 20% less in the tibialis anterior compared with omnivores.
  • β-Alanine intake among 29 omnivorous males was 0.332 ± 0.144 g/day. Among these omnivores there was no correlation between β-alanine intake and carnosine concentrations.
  • Some CNDP1 genotypes were associated with higher carnosinase activity. However, a correlation was not detected between muscle carnosine levels and activity of the carnosine-degrading enzyme.

Interpretation of findings/Key practice applications

It may be advised that vegetarian athletes consume a β-alanine supplement in order to increase their carnosine concentrations. However, this study did not examine the research questions that omnivores would benefit from β-alanine supplementation in regard to muscle carnosine levels or performance. Females were characterized to have lower levels of carnosine than males, but they also have higher levels of plasma carnosinase activity, so it is unknown if higher β-alanine intake could shift the equilibrium.

Limitations

The authors mention that the type of muscle fibers (i.e. fast-twitch or slow-twitch) may partially be responsible for the different carnosine concentrations in females vs. males. It would be interesting to see if how different types of training affect carnosine concentrations within each gender group.
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