Metabolomic profiling for identification of metabolites and relevant pathways for taurine in hepatic stellate cells

Table 1 Gradient elution program of the mobile phase

Time (min)	Flow rate (mL/min)	Solution B (%)
0	0.35	5
1	0.35	5
6	0.35	20
9	0.35	50
13	0.35	95
15	0.35	95

Table 2 Potential important biological metabolites in ESI⁺ and ESI^- modes for taurine in hepatic stellate cells

Number	Mode	VIP	RT (min)	m/z ratio	Compound name	Fold change (B/A)	P value
1	ESI+	1.312	11.16	495.3338	PC (16:0)	-0.758↓	0.037
2	ESI+	1.973	14.02	148.0160	2-oxo-4-methylthiobutanoic acid	-3.094↓	0.001
3	ESI+	1.326	7.51	215.1890	Amino-dodecanoic acid	1.249↑	0.043
4	ESI+	1.316	3.89	231.1475	Butyryl-L-carnitine	-1.711↓	0.041
5	ESI+	1.644	8.87	273.2679	C16 Sphinganine	-0.837↓	0.034
6	ESI+	1.329	0.74	161.1047	Carnitine	2.324↑	0.049
7	ESI+	1.570	13.27	375.3125	Docosatetraenoyl Ethanolamide	2.200↑	0.017
8	ESI+	1.706	11.46	399.3362	Palmitoylcarnitine	-1.419	0.005
9	ESI+	1.484	11.01	199.1943	Dodecanamide	1.521↑	0.022
10	ESI+	1.590	1.09	307.0848	Glutathione	-1.372↓	0.019
11	ESI+	1.268	6.03	259.1792	Hexanoylcarnitine	-1.216↓	0.046
12	ESI+	1.565	4.59	282.1684	Hydroxydesipramine	2.210↑↓	0.013
13	ESI+	1.601	11.01	569.3486	LysoPC(22:5)	17.551↑	0.048
14	ESI+	1.483	1.01	175.0482	N-acetylaspartate	-1.160↓	0.018
15	ESI+	1.495	12.63	369.3254	N-palmitoyl isoleucine	1.375↑	0.017
16	ESI+	1.557	12.15	369.3254	N-palmitoyl isoleucine	2.683↑	0.039
17	ESI+	1.245	10.48	371.3045	N-stearoyl serine	-1.027↓	0.048
18	ESI+	1.312	13.05	281.2728	Oleamide	-0.852↓	0.036
19	ESI+	1.469	10.13	212.1417	Oxo-dodecenoic acid	1.750↑	0.019
20	ESI+	1.595	11.24	479.3025	PC (15:1)/PE (18:1)	-1.141↓	0.018
21	ESI+	1.284	11.30	521.3494	PC (18:1)	-0.727↓	0.048
22	ESI+	2.021	8.93	317.2939	Phytosphingosine	-1.274↓	0.001
23	ESI+	1.290	0.65	202.2163	Spermine	-0.874↓	0.039
24	ESI+	1.443	9.90	301.2992	Sphinganine	-0.807↓	0.040
25	ESI+	1.394	11.60	299.2835	Sphingosine	-0.949↓	0.026
26	ESI+	1.430	12.34	427.3675	Stearoylcarnitine	-1.006↓	0.026
27	ESI+	1.818	0.80	117.0791	Valine	-0.681↓	0.037
28	ESI-	2.017	1.13	192.0270	Citric acid	-0.870↓	0.001
29	ESI-	1.678	11.11	453.2859	Glycerophospho-N-Palmitoyl Ethanolamine	-1.125↓	0.011
30	ESI-	2.076	11.46	479.3016	PC (15:1)	-1.697↓	0.000
31	ESI-	1.648	0.69	264.1045	Thiamine	0.394↑	0.040
32	ESI-	1.448	9.25	250.1204	Ubiquinone-1	1.538↑	0.031

Comparisons were done by two-sample t-test. A total of 27 metabolites in ESI⁺ mode and 5 metabolites in ESI^- mode were found to be the significant metabolites between the control and taurine-treated cells (VIP > 1) (P < 0.05). PC: Phosphatidylcholine; VIP: Variable importance in the projection; (↑): Up-regulated; (↓): Down-regulated.

Table 3 Results of MetPA pathway analysis

Pathway name	Compounds1	Expected2	Hits	Raw P3	FDR P4	Impact
Glutathione metabolism	38	0.23681	2	0.022	0.896	0.272
Sphingolipid metabolism	25	0.1558	3	0.000	0.033	0.231
Thiamine metabolism	24	0.14956	1	0.140	1	0.125
Citrate cycle (TCA cycle)	20	0.12464	1	0.118	1	0.063
Valine, leucine and isoleucine biosynthesis	27	0.16826	1	0.156	1	0.013
Cysteine and methionine metabolism	56	0.34898	2	0.046	1	0.009
Glyoxylate and dicarboxylate metabolism	50	0.31159	1	0.271	1	0.003
Glycerophospholipid metabolism	39	0.24304	1	0.218	1	0.003

¹The total number of metabolites in each pathway;

²The actually matched number according to the uploaded data;

³The original P-value using enrichment analysis;

⁴The adjusted P-value using false discovery rate. The table shows the detailed results from the pathway analysis. Since we tested many pathways at the same time, the P-values from enrichment analysis are further adjusted for multiple tests. In particular, the Hits is the actually matched number from the user uploaded data; the Raw P is the original P-value calculated from the enrichment analysis; the FDR P is the P-value adjusted using false discovery rate; the Impact is the pathway impact value calculated from pathway topology analysis. Sixteen potential metabolic pathways were analyzed by MetPA network software and three significant metabolic pathways (Sphingolipid metabolism, glutathione metabolism and thiamine metabolism) were found to be the most important metabolic pathways for taurine in HSCs; HSCs: Hepatic stellate cells.