Clinical Urinary Peptidomics: Learning to Walk Before We Can Run

Abstract

The “urinary peptidome” promises to be a resource at least as dynamic and informative as the “urinary proteome”. Given that neither approach has so far given up many clinical pearls, this may not be saying much. But one likely pathway for urinary peptidomics is set out in the paper by Fiedler et al. (1) in this issue of Clinical Chemistry . These workers have combined high-throughput technology with a study of the basic problems that will need to be overcome to transform a promising approach into something more durable. Although they are not the first to use some of the techniques (2)(3), and although numerous problems remain, this study is required reading for all those interested in this area. Urine, as a matrix, must be one of the least desirable biological fluids for both peptidomic and proteomic work. It is important to recall some basic biology: The composition of urine is by its design highly variable. Indeed the variability of its composition is a major way in which the “ milieu interieur ” is kept more or less constant in the face of environmental and nutritional changes. Urine volume, salt composition and pH can, and do, vary widely in health. In disease there is frequently proteinuria and, if that were not enough, urine is often infected even in apparently healthy individuals. Having said that, urine is also the source of one …