. 2021 Nov;32(11):2877–2884. doi: 10.1681/ASN.2021030336

Table 3.

Metabolomic analysis of solute secretion

Solute	Fractional Clearance [Free]		Free Fraction		Fractional Clearance [Total]
Solute	Control	CKD/Control	Control	CKD/Control	Control	CKD/Control
1,3,7-Trimethylurate	15.1±5.5	0.76	1.48±0.72	0.6	23.9±9.8	0.76
3-Indoxyl sulfate	14.2±4.8	0.43^a	0.03±0.01	2.1^a	0.5±0.1	0.85
Pyridoxate	13.1±7.8	0.60
N-(2-furoyl)glycine	11.8±8.1	0.34
Guanidinoacetate	10.1±8.5	0.87	1.16±0.26	0.9	13.9±9.9	0.52
3-Hydroxyhippurate	9.7±6.3	0.93	0.39±0.13	1.2	4.8±3.3	0.86
5-Acetylamino-6-formylamino-3-methyluracil	9.6±5.0	0.64	1.32±0.49	0.7	14.8±6.2	0.37^a
4-Methylcatechol sulfate	8.7±4.0	0.29^a	0.04±0.01	2.6^a	0.4±0.1	0.70
5-Hydroxy-2-methylpyridine sulfate	7.8±5.6	0.28	0.17±0.07	1.8	1.9±0.9	0.31^a
Hippurate	7.5±2.7	0.83	0.29±0.07	1.5	2.7±1	1.08
1,7-Dimethylurate	6.4±1.7	0.94	0.29±0.08	1.5^a	2.3±0.5	1.20
4-Hydroxyhippurate	6.2±2.5	0.85	0.46±0.14	1.1	3.4±1.4	0.88
N2,N5-diacetylornithine	6.1±3.0	0.43^a	0.99±0.31	0.9	7.5±3.6	0.32^a
p-Cresol sulfate	5.8±1.2	0.65^a	0.04±0.01	1.6^a	0.3±0.1	0.96
N-acetyl-2-aminooctanoate^b	5.6±4.6	0.46	0.09±0.02	2.2^a	0.5±0.4	0.90
Glutamine conjugate of C7H12O2^b	5.2±1.9	0.54	0.54±0.16	1.2	3.5±1.1	0.55^a
N2,N2-dimethylguanosine	5.2±1.0	0.63^a	0.57±0.07	1.2	3.7±0.5	0.70^a
3-Methyl catechol sulfate (1)	5.1±1.9	0.59	0.03±0.01	1.7^a	0.2±0.1	0.55
2-Isopropylmalate	5.0±4.1	0.88	0.43±0.23	1.4	3.1±2.6	0.79
Acisoga	5.0±3.2	0.84
Vanillylmandelate	4.8±1.0	0.68^a	0.74±0.21	1.1	4.4±1.1	0.67^a
1-Methylnicotinamide	4.8±1.3	1.58	0.85±0.07	1.0	5.2±1.4	1.47
3-Methoxycatechol sulfate (1)	4.7±2.0	0.50^a	0.14±0.04	1.9	0.8±0.2	0.82
1-Methylurate	4.6±1.4	0.78	0.56±0.13	1.2	3.1±1.1	0.84
N-acetylasparagine	4.6±1.6	0.27^a	0.8±0.34	0.8	4.3±2.3	0.19^a
4-Guanidinobutanoate	4.5±1.7	0.47^a	0.85±0.28	1.1	4.9±3	0.36^a
Guaiacol sulfate	4.5±1.2	0.49^a	0.15±0.04	1.7^a	0.8±0.3	0.72
p-Cresol glucuronide^b	4.3±1.2	0.52^a	0.63±0.13	1.3	3.5±1.4	0.57^a
2,6-Dihydroxybenzoic acid	4.1±1.9	0.83	0.16±0.04	1.4	0.8±0.4	1.02
Phenylacetylglutamine	4.0±1.1	0.73	0.69±0.07	1.1	3.4±0.8	0.71^a
Hexanoylglutamine	4.0±1.5	0.57^a	0.54±0.18	1.3	2.5±0.8	0.66^a
1-Methylxanthine	3.9±1.6	0.60
N-acetyltaurine	3.7±0.9	0.49^a	0.33±0.15	1.7^a	1.7±0.6	0.69
Glutamine conjugate of C6H10O2 (1)^b	3.5±0.7	0.50^a	0.62±0.19	1.3	2.6±0.8	0.57^a
N-acetylglucosamine/N-acetylgalactosamine	3.4±1.0	0.97	0.9±0.17	1.1	3.7±0.9	0.95
4-Hydroxyphenylacetylglutamine	3.4±0.9	0.45^a	0.69±0.17	1.1	3±0.9	0.42^a
1-Methyl-5-imidazoleacetate	3.3±2.4	0.28^a	0.95±0.2	0.9	3.7±2.2	0.24^a
Glutamine conjugate of C6H10O2 (2)^b	3.3±1.2	0.61^a	0.62±0.18	1.2	2.4±1	0.67
3-Aminoazepan-2-one	3.2±0.6	1.3^a	0.88±0.14	1.0	3.5±0.7	1.15

Solutes identified as secreted in the metabolomic analysis are listed in order of their average estimated fractional clearance values expressed in terms of the free solute levels in the control participants, denoted fractional clearance [free]. CKD/control is the ratio of the average value in the patients with CKD to the average value in the control participants.

^aP=0.05 for the corresponding value in patients with CKD compared with the value in control participants. The free fraction represents the proportion of solute that is not bound to protein and was calculated as the free level divided by the total level for each solute. Fractional clearance [total] gives the averaged estimated fractional clearance values expressed in terms of the total plasma solute levels in the control participants.

^bA compound whose identity is considered known but has not been confirmed by use of a chemical standard.