Serum creatine, creatinine and total homocysteine concentration-time profiles after a single oral dose of guanidinoacetic acid in humans

Abstract

Guanidinoacetic acid (GAA) is a suitable feed additive yet its possible application in human nutrition as a food supplement requires preliminary pharmacokinetics data. The aim of the present study was to explore the effects of an acute oral dose of GAA on serum GAA, creatine (Cr), creatinine (Crn), and total homocysteine (T-Hcy) concentration-time profiles and urinary excretion rates of GAA, Cr and Crn. Twenty-four young healthy participants (age 22.3±1.3years; 12 males and 12 females) voluntarily ingested a single dose of GAA (2.4g) or placebo (inulin) followed by the serial measurement of serum GAA, Cr, Crn and T-Hcy and urinary GAA, Cr and Crn concentration within the next 24h. In response to GAA ingestion a substantial rise in serum GAA and Cr concentration was observed occurring 1h after the ingestion (peak value of 144.9±24.8μmol/L and 65.5±18.6μmol/L, respectively). The Crn serum profile for 24h was not affected by 2.4g GAA ingestion, showing a peak value of 90.1±12.2μmol/L 1h post-administration. A single dose of GAA induced a notable rise in serum T-Hcy by about 40%. The peak value was observed 12h post administration (13.1±2.1μmol/L). Urinary excretion for GAA and Cr peaked after 4h (453.1±235.0mg/L and 40.8±33.3mg/L, respectively). Crn excretion in urine remained unchanged after GAA administration. In conclusion, orally ingested GAA was readily bioavailable and was transformed to Cr. Serum T-Hcy kinetics proofed to be sensitive to acute GAA intake. Trial identification: clinicaltrials.gov number NCT01133899.