Untargeted metabolomics characteristics of nonobese nonalcoholic fatty liver disease induced by high-temperature-processed feed in Sprague-Dawley rats

BACKGROUND Nonalcoholic fatty liver disease (NAFLD) has become one of the most common chronic liver diseases in the world. In our early clinical data and questionnaire analysis of NAFLD, it was found that the body mass index of some patients did not meet the diagnostic criteria for overweight or obesity. The consumption of high-temperature-processed foods such as fried food, hot pot and barbecue is closely related to the occurrence of nonobese NAFLD. Reducing the intake of this kind of food can reduce disease severity and improve prognosis. AIM To explore the untargeted metabolomics characteristics of nonobese nonalcoholic fatty liver disease in Sprague-Dawley rats induced by high-temperature-processed feed. METHODS Fifty-four male Sprague-Dawley rats were divided into three groups: The control group received a standard diet; the nonfried soybeans (NDFS) group received 60% NDFS and 40% basic feed and the dry-fried soybeans (DFS) group received 60% DFS and 40% basic feed. Six rats were sacrificed at week 4, 8, and 12 in each group. The food intake, body weight, Lee’s index, liver index, serological index and hepatic histopathology were assessed. Untargeted metabolomics characteristics were used to analyze the changes in liver metabolites of rats at week 12. Correlations between metabolites and pathology scores between the DFS and control groups and between the DFS and NDFS groups were analyzed. We selected some of the metabolites, both within the pathway and outside of the pathway, to explain preliminarily the difference in liver pathology in the three groups of rats. RESULTS There were no statistically significant differences in the food intake, body weight, Lee's index or serological index between the DFS group and the control group (P > 0.05). At week 8 and week 12, the steatosis scores in the DFS group were significantly higher than those in the other two groups (P < 0.05). At week 12, the liver index of the DFS group was the lowest (NDFS group vs DFS group, P < 0.05). The fibrosis score in the DFS group was significantly higher than those in the other two groups (P < 0.05). The correlation analysis of the liver pathology score and differential metabolites in the DFS and NDFS groups showed that there were 10 strongly correlated substances: Five positively correlated substances and five negatively correlated substances. The positively correlated substances included taurochenodeoxycholate-3-sulfate, acetylcarnitine, 20a,22b-dihydroxycholesterol, 13E-tetranor-16-carboxy-LTE4 and taurocholic acid. The negatively correlated substances included choline, cholesterane-3,7,12,25-tetrol-3-glucuronide, nicotinamide adenine dinucleotide phosphate, lysoPC [16:1 (9Z)] and glycerol 3-phosphate. The correlation analysis of the liver pathology score and differential metabolites in the DFS and control groups showed that there were 13 strongly correlated substances: Four positively correlated substances and 9 negatively correlated substances. The positively correlated substances included 4-hydroxy-6-eicosanone, 3-phosphoglyceric acid, 13-hydroxy-9-methoxy-10-oxo-11-octadecenoic acid and taurochenodeoxycholate-3-sulfate. The negatively correlated substances included lysoPC [16:1(9Z)], S-(9-hydroxy-PGA1)-glutathione, lysoPC [20:5 (5Z, 8Z, 11Z, 14Z, 17Z)], SM (d18:1/14:0), nicotinamide adenine dinucleotide phosphate, 5,10-methylene-THF, folinic acid, N-lactoyl-glycine and 6-hydroxy-5-methoxyindole glucuronide. CONCLUSION We successfully induced liver damage in rats by using a specially prepared high-temperature-processed feed and explored the untargeted metabolomics characteristics.