基于昼夜节律的牛奶品质研究

【背景】昼夜节律是生物界普遍经历的自然现象，随着昼夜节律的变化，生物细胞内部发生着不同的反应和变化，并对动物机体的代谢和生理机能也产生不同的影响，进而影响动物的生长、生产和繁殖等活动。牛奶是人类喜爱的接近完美的食物，由于受科技水平的限制，多年来，人们对牛奶的认识仅停留在营养层面，而忽略昼夜节律对牛奶理化特性和生理功能的影响。【目的】通过对昼夜牛奶的理化特性和生理功能研究，提出根据牛奶不同时段的生理功能收集牛奶，为昼夜牛奶的分类加工和科学饮用奠定了理论依据。【方法】分别采集夜间（5:00，产生时间21:00-5:00）和白天(13:00，产生时间6:00-13:00)的牛奶检测其营养组成，并通过脂质组学检测牛奶脂肪酸组成。提取上清液检测牛奶的理化指标，包括超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）、谷胱甘肽还原酶（GR）、丙二醛（MDA）等氧化还原指标；褪黑素（melatonin,MT）、生长激素（GH）、三碘甲状腺原氨酸（T3）、胰岛素（INS）、胰高血糖素（GCN）等代谢相关激素和免疫球蛋白A(Ig A)、免疫球蛋白G(Ig G)、肿瘤坏死因子α(TNF-α)、白介...

Study on Milk Quality Based on Circadian Rhythm

【Background】 Circadian rhythm is a common natural phenomenon undergoing in the biological world. With the change of day-night cycle, there are plenty of diverse reactions and changes taking place in living cells. So does it in animals, circadian rhythm affects the metabolism and physiological function inside the body, and further affects the growth, production, and reproductive of animals. Milk is the popular and near-perfect food in the world. On account of technological limitation, the knowledge on milk is just rested on the nutrition, ignored the physicochemical property and physiological function, especially physicochemical property and physiological function of day and night milk responding to circadian rhythm. 【Objective】 Through the research on the physical and chemical characteristics and physiological function of milk in day and night, it was proposed to collect milk according to the physiological function of milk in different periods, which could lay a theoretical basis for the classification, processing and scientific drinking of milk in day and night. 【Method】 This research collected night milk (5:00, produced from 21:00 to 5:00) and day milk (13:00, produced from 6:00 to 13:00) to detecte milk nutrients composition and fatty acids composition by lipidomics. The tiny molecular composition were investigatued by metabonomics and physicochemical properties antioxidation ability, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), gluathione reductase (GR), malondialdehyde (MDA), and metabolism related hormones, such as melatonin (MT), growth hormone (GH), triiodothyronine (T₃), insulin (INS) and glucagon, as well as immune factors, such as immune globulin A (IgA), immune globulin G (IgG), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interferons-γ (IFN-γ), heat shock protein 70 (HSP70), heat shock protein 90 (HSP90) etc. 【Result】 The milk fat, protein, lactose, and total milk solids were not different between night milk and day milk, but the small molecules, metabolites, lipids, hormones and cytokines differed between day milk and night milk. Night milk was differ from day milk in physicochemical property, for antioxidant activity and immunity activity of night milk were significant high than that of day milk. The content of MT and IFN-γ in night milk were markedly higher than those in day milk, and the content of MDA, heat shock protein (HSP70, HSP90) were significantly increased. The result of metabolomics revealed that there were 36 differential metabolites were detected between night-milk and day-milk. Except 3 of them in night-milk were lower than that of day-milk, the rest 33 in night-milk were higher than that of day-milk. These metabolites were belonging to carbohydrate (such as dihydroxyacetone phosphate, D-glucose 6-phosphate, D-lactose, 2-ethoxyethanol, dihydroxyacetone, acetyl phosphate, acamprosate, alpha-D-glucose, D-galacturonic acid, raffinose, D-sorbitol, cis-aconitate, etc.), lipid (such as DL-α-hydroxybutyric acid, cis-9-palmitoleic acid, stearidonic acid, myristoleic acid, eicosapentaenoic acid, cholic acid, tridecylic acid, myo-inositol, DL-2-aminoadipic acid, etc.), amino acids (such as L-citrulline, D-ornithine, D-proline, taurine, N6-acetyl-L-lysine, N-acetylneuraminic acid, lys-leu, L-alanine, etc; N6-methyl-L-lysine, etc.) and other aromatic compounds (such as S-methyl-5'-thioadenosine, 2'-O-methylcytidine, 2'-deoxyuridine, etc.). Lipidomics analyses showed a total of 21 lipid classes and 1 094 lipid species were detected in the milk samples. The majority of the lipid species were TGs (379), accounts for 34%. These lipids included triglycerides (TG), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), sphingomyelin (SM), ceramide (Cer), O-acyl-ω-hydroxy fatty acid (OAHF), and diacylglycerol (DAG) categories. The composition of the lipids was very different between night milk and day milk. 【Conclusion】 Based on these differents, this research put forward a strategic method on milk classifying, processing, selling and drinking, in an attempt to meet the demands of people at different period and physiological status. This could make full use of the milk physiological property and better serve for human health at the time of providing nutrition and better serve the health of human beings.