Table 3.

The findings of metabolomic researches on NAFLD.

Reference	Methods	Sample	Main findings
[25]	LC-QTOF-MS and GC-QTOF-MS	Serum	α-Ketoglutarate levels are significantly increased in obese patients compared with lean controls.
[26]	UPLC-MS/MS	Serum and urine	Serum and urine DCA concentrations were statistically significantly increased. Patients with NASH exhibited a greater postprandial increase in all bile acid groups except LCA and 6α-hydroxylated bile acids. Patients with NASH had decreased glycine- and taurine-conjugated LCA exposure over the postprandial period.
[27]	CE-TOF-MS and LC-TOF-MS	Serum	Etiocholanolone-S, DHEA-2S, and DHEA-S decreased with the progression of fibrosis, while 16-OH-DHEA-S increased with the progression of fibrosis. The ratio of 16-OH-DHEA-S to DHEA-S (16/D) and the ratio of 16-OH-DHEA-S to etiocholanolone-S (16/E) were more clearly associated with the fibrosis grade.
[28]	UPLC-QTOF-MS/MS	Serum	Strong overlap of the animal model samples and human NAFLD patients is observed in the sn-1 monoacylglycerophosphocholine profile. Seven sphingomyelin type lipids: (SM 36:3), (d18:2/16:0), (d18:2/14:0), (d18:1/18:0), (d18:1/16:0), (d18:1/12:0), and (d18:0/16:0) were found to be significantly altered in the human NAFLD patients compared to normal liver subjects; similar tendencies were also found in the animal model samples. Deoxycholic acid was found significantly higher both in the animal model samples and in the human NAFLD patients.
[29]	GC-MS	Tissue	Hydroquinone (HQ) and nicotinic acid (NA) suggest a protective effect against NAFLD. However, only NA showed marked effects on both steatosis and transaminase levels suggesting its potential as a therapeutic or preventive agent in NALFD.
[30]	HPLC-QTOF-MS	Tissue and serum	Stearoylcarnitine increased notably in both rat liver tissue and serum. However, the potential as biomarker of NAFLD still needs to be confirmed by extensive studies.
[31]	1H-NMR	Serum	Four potential biomarkers for diagnosis of NAFLD stages were selected: serum glucose, lactate, glutamate/glutamine, and taurine. A specific combination of spectroscopic changes in glucose, lactate, glutamate/glutamine, and taurine levels may prove to be an accurate means of noninvasively diagnosing various stages of NAFLD.