Targeted, LCMS-based Metabolomics for Quantitative Measurement of NAD(+) Metabolites.

Nicotinamide adenine dinucleotide (NAD(+)) is a coenzyme for hydride transfer reactions and a substrate for sirtuins and other NAD(+)-consuming enzymes. The abundance of NAD (+), NAD(+) biosynthetic intermediates, and related nucleotides reflects the metabolic state of cells and tissues. High performance liquid chromatography (HPLC) followed by ultraviolet-visible (UV-Vis) spectroscopic analysis of NAD(+) metabolites does not offer the specificity and sensitivity necessary for robust quantification of complex samples. Thus, we developed a targeted, quantitative assay of the NAD(+) metabolome with the use of HPLC coupled to mass spectrometry. Here we discuss NAD(+) metabolism as well as the technical challenges required for reliable quantification of the NAD(+) metabolites. The new method incorporates new separations and improves upon a previously published method that suffered from the problem of ionization suppression for particular compounds.