Glucose resonances (δ 3.25–3.84) were predominant in the liver profile, which was also dominated by high levels of taurine and trimethylamine-N-oxide (TMAO) (Figure 2A and B). The oxidized glutathione (GSSG) pattern was readily identified in the one-dimensional (1D) spectrum. It is possible to differentiate between the reduced (GSH) and the oxidized (GSSG) forms of glutathione by 2D NMR because the resonances of the magnetically non-equivalent protons of the cysteine β-CH2 residue in GSH (δ 2.95) shift to high frequency in GSSG (δ 3.29 and 2.95) (Koga et al, 1986). The statistical model built from all liver spectra displayed an outlier in the GF group (data not shown). This highly dilute sample was removed from the subsequent analysis and the model was recalculated with four individuals in the GF group against five individuals in the conventional group. The metabolite profile of the liver from GF mice exhibited significant higher levels of TMAO and phosphocholine. Not significant higher levels of tauro-conjugated bile acids and glycine were noted in the GF mouse profile (Figure 2C). In addition, a lower level of GSSG together with a higher level of hypotaurine was observed in the liver of two GF animals.