A minimal input-output configuration for a priori identifiability of a compartmental model of leucine metabolism

To develop a model describing the structure and function of a metabolic system using data from an input-output experiment, it is useful to design a pilot tracer study first which contains a predicted maximal amount of information. Having postulated a physiologically reasonable model structure from the pilot data, two questions arise, first, whether the model parameters are a priori uniquely identifiable, and if so, whether the pilot experiment is a minimal one. The purpose of the present study is to determine a minimal input-output configuration for the a priori unique identifiability of a compartmental model describing the metabolism of leucine, an essential amino acid. The original pilot tracer experiment was a two-stage experiment consisting first of a two-input-five-output experiment followed by a single-input-single-output experiment. It is shown that to guarantee a priori unique identifiability of the leucine model, the single-input-single-output experiment is not necessary, and that two of the outputs of the multi-input-multi-output experiment are not required.