The contribution of muscle, kidney, and splanchnic tissues to leucine transamination in humans

The first steps of leucineutilization are reversible deaminationto α-ketoisocaproic acid (α-KIC) and irreversible oxidation. Recently the regulatory role of leucine deaminationover oxidation was underlined in rodents. Our aim was to measure leucine deaminationand reamination in the whole-body, in respect to previously determined rates across organs, in humans. By leucineand KIC isotope kinetics, we determined whole-body leucine deaminationand reamination, and we compared these rates to those already reported across the sampled organs. As an in vivo counterpart of the “ metabolon” concept, we analysed ratios between oxidation to either deaminationor reamination. Leucine deaminationto KIC was greater than KIC reamination to leucinein the whole-body (p=0.005), muscle (p=0.005) and the splanchnicarea (p=0.025).These rates were not significantly different in the kidneys. Muscle accounted for ≈60% and ≈78%, the splanchnicbed for ≈15% and ≈15%, and the kidney for ≈12% and ≈18%, of whole-body leucinede...