乳极性脂质组成及其功能性研究进展

乳中含有2％～5％的脂质,乳中的脂质由乳腺上皮细胞分泌并以乳脂肪球的形式分散在乳中.大部分乳脂(约98％)以甘油酯的形式存在于乳脂肪球内部,其余(约2％)包括甘油磷脂、鞘脂、糖脂等在内的少部分极性脂质则主要分布在乳脂肪球膜表面.乳极性脂质虽然在乳脂中占比较少,但却对哺乳动物的生长发育有着不可或缺的作用.本文首先介绍乳中...     

共轭亚油酸诱导的奶牛低脂乳症中脂肪球膜甘油磷脂的组成差异分析

旨在分析共轭亚油酸(CLA)诱导奶牛低脂乳症对牛乳脂肪球膜甘油磷脂含量的影响.选取体况相近、泌乳中期的10头荷斯坦奶牛进行自身前后对照设计,试验期12 d,第1天至第6天每头牛饲喂基础日粮+CLA 400 g·d-1,第7天至第12天恢复为饲喂基础日粮,每天记录产奶量及采食量,分析乳成分及乳脂肪球(MFG)粒径参数,对...     

Advances on Current Techniques and Methodologies in Milk Lipidomics

Milk is a complex biological fluid containing lipids, proteins, carbohydrates and minerals, which are essential for infant growth. While the lipid portion constitutes only 3％-5％ of the total milk composition, it accounts for over 50％ of the infant's daily energy intake. The dominant portion (approximately 98％) is in the form of triacylglycerols and polar lipids, such as glycerophospholipids and sphingolipids, forming minor components. Recently, with the development of lipidomics, important progresses have been made in milk lipidomics, and the identification and quantification of several milk lipids at the group and molecular species level has become a reality, thereby providing useful information for the infant formula industry. In this review, an overview of the separation of the main components of milk lipids was presented, including glycerolipids, phospholipids and sphingolipids. The analytical methods and strategies for milk lipidomics, including gas chromatography-mass spectrometry (MS), capillary electrophoresis MS, nuclear magnetic resonance, matrix-assisted laser desorption ionization-MS, electrospray ionization-MS, shotgun lipidomics and liquid chromatography-MS, were reviewed. Additionally, the bioinformatics of lipidomics for milk lipid determination, including lipid classification, lipid databases and lipid analysis software, were investigated. This review would aid future investigations of the nutrition of milk lipids and refined researches on formula milk powder.     

Purification and characterization of glycerolipid acyl-hydrolase from the red alga Gracilaria vermiculophylla

ABSTRACT:   A glycerolipid acyl-hydrolase was purified 19-fold with a yield of 11% from the prostaglandin-producing red alga Gracilaria vermiculophylla by ammonium sulfate precipitation, anion-exchange chromatoraphy and gel filtration chromatography. Sodium dodecylsulfate– polyacrylamide gel electrophoresis of the final preparation showed a single band corresponding to a molecular mass of 20 kDa, but Superdex 200 fast protein liquid chromatography exhibited a molecular mass of 40 kDa. Accordingly, it was suggested that the purified enzyme was a homodimer of a 20 kDa subunit. The optimal temperature and pH were 37°C and 7–8, respectively. The purified enzyme catalyzed hydrolysis of the acyl groups of both glycoglycerolipids and phospholipids, especially monogalactosyldiacylglycerol and phosphatidylcholine. These results suggest that the enzyme hydrolyze the membrane lipids of the alga to release various saturated and unsaturated fatty acids, including arachidonic acid as substrate for prostaglandin synthesis.     

Effects of salinity on the fatty acid compositions of total lipid and individual glycerophospholipid classes of Atlantic salmon (Salmo salar) and turbot (Scophthalmus maximus) cells in culture

Cells from a relatively stenohaline marine species, turbot (Scophthalmus maximus) (TF) and an anadromous species, Atlantic salmon (AS) were cultured in media supplemented with NaCl to produce OPs varying from 300 to 500 mOsm kg^–1 and the direct effects of OP (salinity) on the fatty acid compositions of the main glycerophospholipid classes were determined. The most dramatic effects of salinity on total lipid fatty acids were observed in polyunsaturated fatty acids (PUFA) in TF cells. There was a graded decrease in the percentage of 18:2n-9, and consequently total n-9 PUFA, and concomitantly increased percentages of both total n-3 and n-6 PUFA with increasing salinity. The increased n-3 and n-6 PUFA was due to significantly increased percentages of the major fatty acids in each of these groups, namely 22:6n-3 and 20:4n-6, respectively. The reciprocal changes in n-9 PUFA and n-3/n-6 PUFA in TF cell total lipid resulted in the percentage of total PUFA not being significantly affected by changes in salinity. The graded decrease in 18:2n-9 with increasing salinity in TF cells was observed in all the major glycerophospholipids but especially PE, PI and PS. Increasing salinity resulted in graded increases in the percentages of 22:6n-3 in PE and PS in TF cells. The quantitatively greatest increase in the percentage of n-6 PUFA in TF cells occurred with 20:4n-6 in PC, PE and PL. There were less significant changes in the fatty acid compositions of glycerophospholipids in AS cells. However, the proportion of total n-3 + n-6 PUFA in PE varied reciprocally with the proportion of dimethylacetals in response to salinity. Similar reciprocal changes between fatty acids in response to salinity were also evident in the quantitatively more minor glycerophospholipids PS and Pl. In PS, the percentage of 22:6n-3 was significantly lower at 400 mOsm kg^–1 whereas the proportion of total monoenes was significantly higher at that salinity. A similar inverse relationship between total monoenes and 20:4n-6 (and, to a lesser extent total saturates) in response to salinity was noted in PI. The results show that environmental salinity, without whole-body physiological stimuli, has direct effects on the fatty acid composition of major glycerophospholipid classes in fish cells and that these effects differ in cells from different fish speciesAbbreviations ANOVA analysis of variance - BHT butylated hydroxytoluene - BSA bovine serum albumin - DMA dimethylacetals - EMEM Eagle's minimal essential medium - FCS fetal calf serum - GC gas chromatography - HBSS Hank's balanced salt solution (without Ca²⁺ and Mg²⁺) - OP osmotic pressure - PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PS phosphatidylserine - PUFA polyunsaturated fatty acid - TLC thin-layer chromatography