Table 3.

Relative concentrations and¹³C enrichments of glutathione.

moiety	Chemical shift	#1	#2	#3	#4	#5	#6	#7	#8
GSSG-Gly C2	44.5 ppm	0.23	0.44	0.97	0.55	1.20	0.74	0.52	0.86
enrichment (%)		0.45	0.82	0.63	0.60	0.78	0.60	0.17	0.58
GSH-Gly C2	44.4 ppm	0.84	0.18	0.04	0.38	0.09	0.25	0.08	0.17
enrichment (%)		0.47	0.56	0.60	0.70	0.57	0.60	NDa	0.55
Sum (Gly moiety C2)		1.07	0.62	1.01	0.93	1.29	0.99	0.60	1.03
GSSG-Cys C3	39.8 ppm	0.12	0.12	0.39	0.24	0.60	0.39	0.34	0.35
GSH-Cys C3	26.7 ppm	0.75	0.09	0.04	0.04	0.08	0.04	0.02	0.11
Sum (Cys moiety C3)	0.87	0.21	0.43	0.28	0.68	0.43	0.36	0.46
GSSG-Glu C4	32.5 ppm	0.14	0.23	0.52	0.26	0.59	0.32	0.43	0.38
enrichment (%)		ND	ND	0.77	0.20	0.06	ND	ND	ND
GSH-Glu C4	32.5 ppm	0.80	0.18	0.22	0.32	0.24	0.20	ND	0.19
enrichment (%)	0.07	ND	0.59	0.20	ND	ND	ND	ND
Sum (Glu moiety C4)	0.94	0.41	0.74	0.58	0.83	0.52	0.43	0.57
GSSG-Glu C3⸹	27.4 ppm	0.06	0.06	0.75	–	0.83	0.47	–	0.42
enrichment (%)		ND	ND	0.45	–	0.96	0.92	–	1.09
GSH-Glu C3	27.4 ppm	0.87	0.15	0.07	–	0.07	0.30	ND	0.14
enrichment (%)		0.45	0.58	ND	–	ND	ND	ND	ND
Sum (Glu moiety C3)		0.93	0.21	0.82	–	0.90	0.77	–	0.56

The relative concentration of glutathione was based on singlet signals from the carbons of component amino acids, glycine (Gly), cysteine (Cys) and glutamate (Glu), normalized by the signal of DSS. Excess ¹³C enrichment was calculated using a doublet from glycine moiety C2, glutamate moiety C3 and C4 in glutathione by assuming a singlet from the corresponding carbon as natural abundance. Since the amount of tissue collected through a biopsy varied among participants, the concentration of glutathione was calculated for 1 g. ¹³C enrichments in glutathione cannot be directly compared among participants because the interval from [U–¹³C₃]glycerol administration to a liver biopsy varied.

^aND, not detected; ^⸹Due to overlap with glutamine C3, the quantitation of glutamate moiety C3 could be not-precise.