From QC to Quantitation: Utility of QReSS™ Metabolites in FBS Measurements

Introduction

Metabolomics is a rapidly growing field of research that has unique and proven advantages in systems biology and biomarker discovery. Great advances have been made over the past decade on the feasibility of mass spectrometry (MS)-based metabolomics. Despite the advancements, there remains a pervasive need for quality control (QC) as metabolomic experiments can experience unwanted variations that threaten the quality of the acquired data.^1,2 The use of reliable QC measures is therefore critical to assess and prevent unwanted preanalytical and instrumental variation.³ Any system errors or outliers identified through QC testing must therefore be corrected to ensure consistent and meaningful metabolomics data.

An area of metabolomics garnering great interest, particularly in discovery efforts, is the profiling and quantitation of cell cultures. In this in vitro application, fetal bovine serum (FBS) is commonly used as a supplemental growth medium. FBS contains several nutritional and macromolecular components, including a variety of small molecules (e.g., amino acids, carbohydrates, lipids, hormones) that are essential for cell growth and proliferation. FBS from different commercial sources, or handled under different processing techniques (i.e., dialyzed, heat-inactivated, unprocessed), may result in inconsistent cell culture phenotypes and growth rates. Incorporating reliable QCs in the evaluation of FBS, when applied in metabolomics to spent and control media, can help increase the overall confidence of interpretations when this supplemental material possesses variation.

Here, the QReSS™ standard mixes (MSK-QReSS1 and MSK-QReSS2) were used in the QC of metabolites from variably sourced FBS samples. The QReSS standards are beneficial for QC assessments because they comprise a chemically diverse set of 18 stable isotope-labeled metabolites that span a broad molecular weight range, possess varied ionization propensities, and cover a distribution in class and retention time. Highlighted in addition to the QC results is the absolute quantitation of known compounds from targeted MS experiments and novel findings from an untargeted workflow.