title: Guanidinoacetic acid loading affects plasma γ-aminobutyric acid in healthy men.
abstract: OBJECTIVE
  Guanidinoacetic acid (GAA), a precursor of creatine and an innovative dietary agent, activates γ-amino butyric acid (GABA) receptors yet clinical effects of dietary GAA on GABA metabolism are currently unknown. The main aim of this pilot research was to investigate whether GAA loading affected peripheral GABA homeostasis in healthy humans.
  
  
  METHODS
  Eight healthy male volunteers aged 22-25 years were randomized in a double-blind design to receive either GAA (three grams daily) or placebo by oral administration for 3 weeks. At baseline and after 3 weeks participants provided fasting blood samples for free plasma levels of GABA, GAA, creatine and glutamine.
  
  
  RESULTS
  Following 3 weeks of intervention, plasma GABA level dropped significantly in participants receiving 3 g of GAA per day as compared to the placebo (P = 0.03). GAA loading significantly decreased plasma GABA by 88.8 nmol/L (95% confidence interval; 5.4-172.1) after 3 weeks of intervention as compared to the baseline (P = 0.03). GAA intervention positively affected both plasma GAA and creatine (P < 0.05), while no effects of intervention were reported for plasma glutamine.
  
  
  CONCLUSIONS
  Results indicate that supplemental GAA affects peripheral GABA metabolism, and potentially down-regulates GABA synthesis in peripheral tissues. Possible GABAergic action of dietary GAA adds to the safety profile of this novel dietary supplement.
authors: Center for Health, Exercise and Sport Sciences, Stari DIF, Deligradska 27, 11000, Belgrade, Serbia, sergej.ostojic@chess.edu.rs.
authors: Sergej M
authors: SM
authors: Ostojic
authors: Marko
authors: M
authors: Stojanovic
mesh_terms: D000284:Administration, Oral; D000328:Adult; D003401:Creatine / Q000097:blood; D019587:Dietary Supplements; D004311:Double-Blind Method; D015536:Down-Regulation; D005215:Fasting; D005973:Glutamine / Q000097:blood; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D008297:Male; D010865:Pilot Projects; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000097:blood*
chemical_list: D005973:Glutamine; D005680:gamma-Aminobutyric Acid; C004946:glycocyamine; D003401:Creatine; D005998:Glycine