No effect of ornithine alphaketoglutarate on nitrogen excretion or urea synthesis rate in healthy male subjects

SummaryBackground & aimsOrnithine alphaketoglutarate (OKG) is known for its anabolic and anticatabolic effects. Little is known about its effect on proteolysis. We studied urea formation and nitrogen excretion rates following OKG supplementation in healthy volunteers.MethodsSixteen male subjects were kept on a diet stable in protein (1 g kg−1 d−1) and aimed at maintaining body weight. They received oral supplementation of OKG (10 g) or an isonitrogenous placebo (l-alanine) from days 4 to 6 in single daily doses in a randomised, blinded fashion. Urea kinetics were studied on day 4 from plasma urea enrichments following an oral [13C]urea bolus. Nitrogen excretion was assessed from 24-h urine collections prior to supplementation, on day 4 and day 7.ResultsMean urea rate of appearance was 380±86 and 353±120 μmol kg−1 h−1 in the OKG and placebo group, respectively (p=0.62). There were no significant differences in 24-h nitrogen excretion data between groups, neither at separate time points, in overall values (p=0.40) nor in development over time (p=0.53).ConclusionsA single oral dose of OKG did not affect urea production rate differently than the alanine placebo. OKG supplementation led to a temporary increase in nitrogen excretion, as did administration of placebo.