LC-MS/MS Based Metabolomics Reveal Candidate Biomarkers and Metabolic Changes in Different Buffalo Species

SIMPLE SUMMARY: Milk and dairy products have become the most common and an essential nutrition in human life, while dairy products with high nutritional value are attracting more and more attention. Buffalo milk contains higher protein, fat, lactose, and total solid contents and has been considered as the source of superior dairy products, such as mozzarella cheese, butter, ice cream, and yoghurt. Moreover, buffalo milk contains more unsaturated fatty acids (UFAs) which are important for human health owing to their desirable physiological effects. However, the composition of milk seems to vary among different buffalo species and inadequate information is available about the underlying mechanism. Therefore, exploring the biomarkers of superior buffalo milk is crucial for the process of dairy products and buffalo breeding. In the present study, diverse significantly different metabolites were identified among the Mediterranean, Murrah, and crossbred buffalo, and the different metabolites were mainly enriched in fat synthesis related pathways which affected the end fat content in the milk. Moreover, these specific metabolites can be used as candidate biomarkers in the identification of milk quality and molecular breeding of high milk fat buffalo. ABSTRACT: Consumers have shown more and more interest in high-quality and healthy dairy products and buffalo milk is commercially more viable than other milks in producing superior dairy products due to its higher contents of fat, crude protein, and total solids. Metabolomics is one of the most powerful strategies in molecular mechanism research however, little study has been focused on the milk metabolites in different buffalo species. Therefore, the aim of this study was to explore the underlying molecular mechanism of the fatty synthesis and candidate biomarkers by analyzing the metabolomic profiles. Milk of three groups of buffaloes, including 10 Mediterranean, 12 Murrah, and 10 crossbred buffaloes (Murrah × local swamp buffalo), were collected and UPLC-Q-Orbitrap HRMS was used to obtain the metabolomic profiles. Results showed that milk fatty acid in Mediterranean buffalo was significantly higher than Murrah buffalo and crossbred buffalo. A total of 1837/726 metabolites was identified in both positive and negative electrospray ionization (ESI±) mode, including 19 significantly different metabolites between Mediterranean and Murrah buffalo, and 18 different metabolites between Mediterranean and crossbred buffalo. We found 11 of the different metabolites were both significantly different between Mediterranean vs. Murrah group and Mediterranean vs crossbred group, indicating that they can be used as candidate biomarkers of Mediterranean buffalo milk. Further analysis found that the different metabolites were mainly enriched in fat synthesis related pathways such as fatty acid biosynthesis, unsaturated fatty acid biosynthesis, and linoleic acid metabolism, indicating that the priority of different pathways affected the milk fat content in different buffalo species. These specific metabolites may be used as biomarkers in the identification of milk quality and molecular breeding of high milk fat buffalo.