Determination of lipid profiles of Dezhou donkey meat using an LC-MS-based lipidomics method

Intramuscular fat (IMF) is an important factor affecting meat quality, but lipid and metabolic profiles of donkey meat remain unclear. The present study was conducted to investigate lipid characteristics in different parts of Dezhou donkey using lipidomics. The results show that IMF was more abundant in longissimus dorsi muscle (LDM) than rump muscle (RM) and hamstring muscle (HM), and mainly composed of triglycerides (TGs) rich in saturated fatty acid (SFAs) and monounsaturated fatty acid (MUFAs). A total of 1143 lipids belonging to 14 subclasses were identified in donkey meat, of which 73 lipids (23 upregulated and 50 downregulated) including glycerolipids (GLs), glycerophospholipids (GPs) and sphingolipids (SPs) were significantly different and are therefore potential biomarkers in LDM versus RM versus HM analyses (variable importance in projection >1, p < 0.05). Notably, 21 TGs upregulated in LDM were rich in MUFAs at sn-1 and SFAs at 2 and 3 positions of TG. Donkey muscle accumulated far more SFAs at the sn-3 position of TG, while more SFAs were present at the sn-1 positions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), and the percentages of SFAs at the three positions in TG, PC, and PE in the LDM group were much higher. The abundance of MUFAs at the sn-2 positions of TG, PC, and PE was significantly greater than in sn-1 or 3 positions, and the percentages of 18:1n-9 at the sn-1 and 2 position of TGs in LDM were significantly higher than in RM and HM groups. Polyunsaturated fatty acids (e.g.,18:2n-6, 18:3n-3, and 20:4n-6) tended to occur at the sn-1 position in TG, but at the sn-2 position in PC and PE. Significantly differential lipids were mainly enriched in GP, GL, and SP pathways, all considered key pathways for regulating IMF. The results reveal the components, structures and metabolic pathways of lipid molecules in donkey meat, and provide novel insight into the development of donkey meat products and accurate regulation of IMF. PRACTICAL APPLICATION: Intramuscular fat (IMF) is an important factor affecting meat quality, which is directly related to meat flavor, juiciness, and tenderness, but lipid and metabolic profiles of IMF remain unclear. The current results provide basic information for the development of donkey meat products, and broaden our understanding of the regulation of IMF.