南极磷虾油中的脂质种类繁多，包括磷脂（PL）、三酰甘油（TAG）、二酰甘油（DAG）、单酰甘油（MAG）和游离脂肪酸（FFA）。磷虾油的脂质成分通常受季节变化、年际环境变化、捕捞站、储存条件等因素的影响。各种研究表明，EPA和DHA以磷脂形式存在的活性优于其他形式。功能性饮料是滋补品市场上常见的形式之一。脂质由于其脂溶性的特性，通常不能直接开发成功能饮料。脂类在水中相对稳定的分散体通常需要大量的乳化剂。此外，所得到的乳化液体积较大，不易被吸收。有趣的是，磷脂由于其亲水特性，不需要乳化剂就可以制成脂质体。脂质体可以延长功能成分在体内的持久性，在食品部门和医药工业中得到了广泛的应用。
磷虾油独特的生物活性与消化吸收之间有密切联系。TAG和PL在小肠中的消化和吸收方式不同，TAGs在胆汁盐的乳化作用下被消化吸收，而PL可自发形成胶束，在水体环境中运输。脂肪酸通常在胰岛脂肪酶的作用下，从摄入TAG的sn-1和sn-3位置释放出来。PL主要由胰腺磷脂酶A2（PLA2）水解，从sn-2位置释放出脂肪酸，形成衍生的溶酶磷脂。释放出的脂肪酸和溶磷脂被肠道细胞吸收后，部分溶磷脂被肠道细胞衍生的溶磷脂酶进一步水解成脂肪酸和甘油磷胆碱。但是，各种溶酶磷脂与不同的脂肪酸种类的去向尚未见报道。目前，富含DHA/EPA的膳食磷脂的具体消化吸收机制尚不清楚。南极磷虾油磷脂脂质体在体内的吸收动力学尚未阐明，限制了其独特生物活性相关分子机制的分析。因此，中国海洋大学的Lin Li、Xiaoming Jiang、Yuming Wang等在本研究中观察了单次灌服磷脂体形式的南极磷虾油磷脂（AKOP）的健康小鼠血液和消化道中的消化吸收特点。
Results
Conclusion
本研究采用冷丙酮法从南极磷虾油中分离出磷脂，去除三酰甘油，得到了南极磷虾油中的磷脂。所得南极磷虾油磷脂的主要类型为磷脂，其中DHA和EPA总含量为29.31%。本研究对南极磷虾油磷脂脂质体口服后的血清、小肠内容物和肠壁中的脂质进行了分析，以说明其在健康小鼠血液和消化道中的吸收动力学，并通过单次给药的方式说明其在健康小鼠血液和消化道中的吸收动力学。结果显示，AKOP磷脂脂质体在小肠中1 h内几乎完全消化，水解产物可被肠道细胞迅速吸收。此外，血清中的DHA在给药后2 h内达到峰值。本研究结果可能为南极磷虾油磷脂的独特生物活性的分子机制提供科学依据。
The absorption kinetics of Antarctic krill oil phospholipid liposome in blood and the digestive tract of healthy mice by single gavage
Lin Lia，Chengcheng Wanga，Shan Jianga，Rong Lia，TiantianZhanga，Changhu Xueab，Teruyoshi Yanagitac，Xiaoming Jianga，YumingWangab
aCollege of Food Science and Engineering, Ocean University of China, No.5 Yushan Road, Qingdao, 266003, PR China
bLaboratory for Marine Drugs and Bioproducts, Pilot National Laboratory for Marine Science and Technology, Qingdao, 266237, Shandong Province, PR China
cLaboratory of Nutrition Biochemistry, Department of Applied Biochemistry and Food Science, Saga University, Saga, 840-8502, Japan
Abstract
Antarctic krill (Euphausia superba) oil has been gaining increasing attention due to its nutritional and functional potentials. Krill oil usually contains a high concentration (about 50%) of phospholipids (AKOP) rich in DHA and EPA accompanied with 30%–40% triacylglycerols. Phospholipids can be made into liposomes without emulsifiers due to its amphiphilic characteristics. However, the absorption kinetics of AKOP liposome in vivo is not clear, which restrict the molecular mechanism analysis related to its distinct bioactivities. The lipid analysis in serum, small intestinal content and wall was carried out after oral administration of AKOP liposome to illustrate its absorption kinetics in blood and the digestive tract of healthy mice by single gavage. The major type of the obtained AKOP was phosphatidylcholine, and the total contents of the DHA and EPA were 29.31%. AKOP liposome was almost completely digested in the small intestine in 1 h and the hydrolysis products could be quickly absorbed by intestinal enterocytes. The DHA in serum peaked at 2 h after administration of AKOP liposome. AKOP liposome could be quickly digested and absorbed in vivo. The obtained results might provide a scientific basis for the molecular mechanism analysis related to distinct bioactivities of Antarctic krill oil phospholipid.
