Quantitative lipidomics reveals the changes of lipids and antioxidant capacity in egg yolk from laying hens with fatty liver hemorrhagic syndrome

ABSTRACT: In laying hens, fatty liver hemorrhagic syndrome (FLHS) is a common metabolic disorder, which can affect egg production and nutritional value. However, the impact of FLHS on the lipid content in egg yolks was not clear. In this study, FLHS model was induced by using high-energy low-protein diet, and the egg quality was evaluated. Egg yolk lipids were quantitatively analyzed by using ultra-performance liquid chromatography-mass spectrometry combined with multivariate statistical analysis. Gene expressions of the lipoprotein were determined by qRT-PCR and antioxidant capacity of the egg yolk were determined by kits. The elevated blood lipids and extensive lipid droplets observed indicated successful establishment of the FLHS model in laying hens. Measurements of egg quality showed that egg yolk weight was increased in the FLHS group. Lipidomics revealed that 1,401 lipids, comprising 27 lipid subclasses in the egg yolk. According to score plots of principal component analysis and orthogonal partial least squares discriminant analysis, different lipid profile was observed between the control and FLHS groups. A total of 97 different lipid species were screen out. Sphingolipid and glycerophospholipid metabolism were identified as key pathways. Free polyunsaturated fatty acids (PUFA) exhibited an increase in the FLHS group (P < 0.05). Notably, the form of PUFAs was changed that the FLHS group showed an increase in triacylglycerol-docosahexenoic acid and triacylglycerol-arachidonic acid in the egg yolk, while triacylglycerol-α-linolenic acid was decreased (P < 0.05). Total superoxide dismutase was decreased in the egg yolks affected by FLHS. Gene expressions of vitellogenin 2 (VTG2), VTG3, very low-density apolipoprotein II and apolipoprotein B were increased in the liver of laying hens with FLHS (P < 0.05). In conclusion, FLHS promoted the lipid transport from the liver to the yolk by upregulating lipoprotein expression, which altered lipid profile, and reduced antioxidant capacity in the yolk. This study provided a foundation for understanding the changes in lipids, lipid transport and lipid antioxidation capacity in egg yolk from laying hens with FLHS.