a, Summary schematic indicating structure of metabolites and routes (oral or intraperitoneal, i.p.) of formation observed in choline challenge studies in mice using the indicated isotope labeled choline. The m/z in plasma observed for the isotopmers of the choline metabolites are shown. b, Plasma levels of d9-metabolites following i.p. challenge with d9(trimethyl)-dipalmitoylphosphatidylcholine (d9-DPPC). c, d9-TMAO production following oral d9-DPPC in mice, following suppression of gut flora with antibiotics (3 weeks), and then following placement (4 weeks) into conventional cages with non-sterile mice (i.e. – “conventionalized”). Data are presented as mean ± SE from 4 independent replicates.