Effect Of Different Animal Milks On Urinary Metabolome And Blood Parameters In Rats

Milk is the white yellowish liquid secreted by the mammary gland under endocrine and neural regulation. Owing to differences in species, habitats and other physiological factors, animal milks contain different nutrients. Published researches have focused more on the analyses of different milk components, physicochemical properties, and functional ingredients but rarely investigated the influence of dairy ingredients on the metabolism from the perspective of the whole body. In this experiment, rats were used as an animal model. Five-week-old SD rats (total of 48 animals) were randomly divided into four groups after 1-week adaptation in our animal facility. They were fed different types of animal milks (namely camel milk group (T group), cow milk group (N group), yak milk group (M) and control group (group C)) for four weeks. Urine samples were collected before the rats were killed, and blood samples were taken after they were killed. Using high performance liquid chromatography-mass spectrometry and ELISA techniques, this study analyzed the urine metabonomes of these animals and quantified some blood indicators of nutrition metabolism, including serum adiponectin, leptin, total cholesterol, serotonin and y-amino butyric acid.Major results:1. By multivariate statistical analysis (PCA and PLS-DA of metabolites identified from the positive and negative ion modes) of the urine metabolomes of rats fed with different animal milks and the control,20,20, and 21 differential metabolites were identified in samples of the camel, cow, and yak groups, respectively, as compared to the control group. Five unique metabolites were identified in the camel group, e.g. N-hydroxy propionamide, N-methyl aniline. Nine unique metabolites were identified in cow milk group, e.g. glutamic acid, N-acetyl-L-arginine. Nine unique metabolites were identified in the yak milk group, e.g. deoxycytidine, thiamine.2. By ELISA analysis of the collected blood samples, significant differences were found between groups. Compared with the control group, the camel milk group had decreased levels of serotonin, adiponectin and y-aminobutyric acid, while leptin and total cholesterol levels increased (P<0.01). The cow milk group exhibited significant reduction in serotonin, adiponectin, leptin, y-aminobutyric acid, while the total cholesterol level increased (P<0.05). The yak milk group showed significantly decreased levels of blood serotonin, adiponectin, leptin, total cholesterol and y-aminobutyric acid (P<0.01).In summary, this study found that different animal milks exerted variable influence on the urine metabolism and some blood indicators in rats. Metabolic pathways that were modified by giving different milk diets to the animals involved in amino acid, lipid, nucleic acid, and intestinal bacterial metabolism. Significant changes in the measured blood indicator levels suggest that the consumption of milk of different compositions can impact the metabolism of the animals. Findings of this study help to provide some reference data for future study.