Table 2. Factor Analysis for Extracellular Metabolites.

	correlation coefficienta,b			correlation coefficienta,b
metabolite	PC1	PC2	metabolite	PC1	PC2
4-aminohippurate	0.948	0.259	trehalose	0.502	0.380
uridine	0.947	0.281	serotonin	0.474	0.049
choline	0.947	0.257	urea	0.468	0.071
2-hydroxybutyrate	0.945	0.273	N6-acetyllysine	0.465	0.044
isopropanol	0.941	0.267	isobutyrate	0.464	–0.242
GTP	0.930	0.268	glutarate	0.449	–0.258
5-hydroxyindole-3-acetate	0.894	0.292	asparagine	–0.446	0.832
isocaproate	0.892	0.206	alanine	–0.445	0.849
cysteine	0.890	0.288	nicotinurate	0.442	0.766
NADH	0.887	0.302	glycerol	–0.438	0.828
dimethylamine	0.882	0.274	threonine	–0.437	0.742
2′-deoxyinosine	0.881	0.265	O-phosphocholine	0.434	0.021
citrate	0.880	0.156	sn-glycero-3-phosphocholine	0.432	0.070
glycine	0.878	0.067	propylene glycol	–0.422	0.057
ethanolamine	0.874	0.296	2-hydroxyisobutyrate	–0.418	0.789
putrescine	0.865	0.225	serine	–0.396	0.705
AMP	0.863	0.081	lysine	0.387	0.832
2-aminobutyrate	0.845	0.198	thymine	0.381	–0.523
NADP+	0.824	0.206	leucine	–0.374	0.862
NADPH	0.818	0.276	glutamine	–0.349	0.677
sucrose	0.817	0.299	proline	–0.346	0.672
O-phosphoethanolamine	0.816	0.291	4-hydroxyphenyllactate	0.337	–0.437
arginine	0.803	0.038	aspartate	–0.326	0.879
nicotinate	–0.803	0.150	riboflavin	–0.307	0.740
creatinine	0.801	0.226	anserine	–0.249	0.539
methanol	0.797	0.252	phenylalanine	–0.238	0.753
myo-inositol	0.792	0.273	hypoxanthine	–0.229	0.503
O-acetylcholine	0.788	–0.027	tryptophan	0.221	0.701
carnitine	0.781	0.237	cystine	–0.210	–0.632
butyrate	0.780	0.264	glycerate	–0.205	–0.680
ethanol	0.748	0.186	phenylacetate	–0.203	–0.636
5-hydroxytryptophan	–0.739	0.603	N-acetylglucosamine	–0.202	–0.578
N-acetylserotonin	0.723	0.124	homocysteine	–0.200	–0.591
4-aminobutyrate	–0.723	0.552	2′-deoxyadenosine	–0.199	0.757
trimethylamine N-oxide	0.719	0.277	uracil	–0.196	-0.540
ATP	0.710	0.276	carnosine	–0.190	–0.543
oxypurinol	0.698	0.262	cystathionine	–0.184	–0.493
urocanate	–0.692	0.000	malonate	–0.182	–0.479
gluconate	0.685	0.134	maleate	0.116	0.911
betaine	–0.675	0.561	isovalerate	–0.114	–0.666
methionine	–0.674	0.552	S-adenosylhomocysteine	–0.110	0.829
creatine phosphate	0.669	0.160	valine	–0.107	0.516
glutathione	0.662	0.014	pyroglutamate	–0.096	0.931
sarcosine	0.661	0.071	biotin	–0.086	–0.463
glutamate	0.655	–0.026	2-phenylpropionate	–0.086	–0.463
pyridoxine	–0.652	0.627	galactose	–0.086	–0.463
pyruvate	–0.648	0.656	3-hydroxybutyrate	–0.086	–0.463
ornithine	0.643	0.113	4-pyridoxate	–0.086	–0.463
lactate	0.643	0.119	UDP-N-acetylglucosamine	–0.086	–0.463
succinate	0.633	0.122	2-hydroxy-3-methylvalerate	–0.086	–0.463
tyrosine	–0.623	0.266	3-aminoisobutyrate	–0.086	–0.463
ADP	0.607	0.067	mannose	–0.086	–0.463
O-phosphoserine	–0.598	0.667	nicotinic acid adenine dinucleotide	–0.086	–0.463
acetoin	–0.575	0.672	xanthosine	–0.086	–0.463
N-acetyltyrosine	0.560	0.055	6-hydroxynicotinate	–0.086	–0.463
melatonin	0.559	0.083	cholate	–0.086	–0.463
3-methylxanthine	0.551	0.209	galactitol	–0.086	–0.463
methylsuccinate	0.544	–0.029	trans-4-hydroxy-l-proline	–0.086	–0.463
isoleucine	–0.544	0.719	glucose	–0.070	0.733
histidine	–0.530	0.595	3-hydroxyisovalerate	0.033	–0.618
t-methylhistidine	–0.529	0.731	adenosine	0.020	0.673
percent total variance				30.37%	21.73%
cumulative percent variance					52.10%

^aSignificance of correlation coefficient set at threshold of 0.4.

^bCorrelation coefficient numbers in bold indicate metabolites for which the statistical relatedness of the variable is most correlated to the PC as indicated by the square of the cosine.