Characterization of diet-dependent metabolic serotypes: Analytical and biological variability issues in rats

This report, the first in a series on diet-dependent changes in the serum m etabolome (metabolic serotype), describes validation of the use of high per formance liquid chromatography (HPLC) separations coupled with Coulometric array detectors to characterize changes in the metabolome. The long-term ai m of these studies is to improve understanding of the effects of significan t variation in nutritive status on physiology and on disease processes. Ini tial studies focus on identifying the effects of dietary (or caloric) restr iction on the redox-active components of rat serum. Identification of compo unds of interest is being carried out using HPLC separations coupled with c oulometric array analysis, an approach allowing simultaneous examination of nearly 1200 serum compounds. The technical and practical issues discussed in this report are related to both analytical validity (HPLC running condit ions, computer-automated peak identification, mathematical compensation for chromatographic drift, etc.) and biological variability (individual variab ility, cohort-cohort variability, outliers). Attention to these issues sugg ests similar to 250 compounds in serum are sufficiently reliable, both anal ytically and biologically, for potential use in building mathematical model s of serotype.