Lipids Component In Maternal-neonatal Plasma And Longitudinal Human Milk

Background Human breast milk is the ideal food to satisfy infants' demands.Milk essential fatty acids and fat-soluble antioxidants,especially vitamin E and carotenoids,are of great importance for offspring growth and cognition development.The positional distribution of fatty acids among triglyceride(sn-1,3 and sn-2)and the stereoisomerization of ?-tocopherol(the natural occurring RRR-?-tocopherol)influence bioavailability in human body.Objective Paired maternal-cord plasma and longitudinal breast milk(colostrum,transitional milk,mature milk)were collected to determine the content and composition of fatty acids,carotenoids and vitamin E with special attention paid to RRR-?-tocopherol.The purpose of the present study was to understand the transfer of lipids component in maternal-offspring dyads during pregnancy and lactation,and to provide references for the estimation of infant demands and establishment of Chinese human milk composition database.Methods Healthy parturients of full-term,singleton delivery were recruited from Xinhua Hospital affiliated to Shanghai Jiao Tong University School of Medicine,Shanghai,China.Plasma and milk samples were collected according to the willingness of subjects.1.Analysis of fatty acids composition and positional distribution: A total of 126 longitudinal human milk from the same mothers(n=42)were taken to determine the content and sn-2 positional distribution of 28 kinds of fatty acids;2.Analysis of carotenoids and vitamin E: Paired maternal-cord plasma(n=37)and longitudinal breast milk samples(n=42)were taken to determine 5 carotenoids(lutein,zeaxanthin,?-cryptoxanthine,?-carotene,lycopene)and 2 tocopherols(?-,?-tocopherol).3.Analysis of the stereoisomer distribution of ?-tocopherol: paired maternal-cord plasma and longitudinal human milk samples were collected from the same mothers(n=50)to determine the content of ?-tocopherol and the distribution of stereoisomers(natural RRR and synthetic RRS,RSR,RSS,?2S).Results 1.The content of total fatty acids in breast milk increased from 15.09 g/L in colostrum to 32.57 g/L in mature milk.The highest content was found in saturated fatty acids as 36.96-40.85%,followed by monounsaturated(32.53-34.95%)and the lowest was polyunsaturated fatty acids(24.85-26.86%);2.The ratio of linoleic acid to ?-linolenic acid(LA/ALA)in breast milk was 19:1 in colostrum and decreased to 16:1 in transitional milk and mature milk.Although the content of long-chain poly-unsaturated fatty acids decreased significantly with lactation,the ratio of arachidonic acid to docosahexaenoic acid(ARA/DHA)remained stable at 1.3:1;3.Palmitic acid and long-chain poly-unsaturated fatty acids with a carbon chain length as 22 were preferentially distributed at the sn-2 position,while unsaturated fatty acids with high content like oleic acid,linoleic acid and ?-linolenic acid were preferentially distributed at the sn-1,3 position.4.The contents of tocopherols and carotenoids in cord plasma were as low as 12.26% and 11.36% the level of maternal plasma,respectively,and the lowest ratio was found in lycopene(5.35%).Significantly positive correlations were observed in plasma tocopherols and carotenoids in maternal-cord dyads;5.Tocopherols and carotenoids in breast milk decreased significantly with the progression of lactation,but tocopherols and the three xanthophylls correlated positively with the total fat content of breast milk at different lactation stages.However,?-carotene and lycopene were not related to milk fat content.6.Cord plasma contained higher ratio of plasma ?-/?-tocopherol than maternal plasma(20.95 vs.15.23,P < 0.001)and colostrum also contained higher ratios of ?-/?-tocopherol than other two stages(7.21,5.29,4.21,respectively).Lutein predominated in cord plasma and transition and mature milk carotenoids(51.53-52.49%),while ?-carotene(31.78%)and lycopene(32.83%)were the main carotenoids in colostrum.7.The ratio of ?-/?-tocopherol in breast milk was positively correlated with milk LA/ALA and carotenoids,and negatively correlated with ARA/DHA.Lutein was negatively correlated with milk LA/ALA.8.RRR-?-tocopherol showed absolute predominance in maternal-cord plasma and milk ?-tocopherol(80.91-85.06%).Among the synthetic forms,the percentage of RRS(5.25-7.36%)was slightly higher than that of other synthetic configurations,and the contents of RSS,RSR and ? 2S were basically the same(2.26-4.20%).The ratios of RRR/(synthetic 2R forms)in the samples were 5.21-7.42,with the highest level found in colostrum and the lowest in cord plasma.9.There were no correlations between plasma and milk ?-tocopherol levels,but maternal plasma RRR% correlated positively with colostrum(r = 0.322,P = 0.022)and maternal plasma non-RRR% correlated positively with transitional milk(r = 0.325,P= 0.030).Conclusions 1.Compared with the global breast milk reports,the present study revealed a high ratio of LA/ALA as(16-19):1 and a middle level of ARA/DHA.Breast milk triglycerides were dominated by OPO(oleic acid-palmitic acid-oleic acid)and OPL(oleic acidpalmitic acid-linoleic acid),while DHA and EPA were preferentially distributed at the sn-2 position.The special structure of milk triglycerides has physiological significances for fatty acids absorption,metabolism and tissue uptake in human body;2.The ratio of ?-/?-tocopherol was higher in cord plasma than the level of maternal plasma and higher in colostrum than the other two stages.?-carotene and lycopene were dominant in colostrum,while lutein was dominant in transitional milk,mature milk and cord plasma.Neonates and infants have varied demands of tocopherols and carotenoidsduring pregnancy and different lactation stages;3.Tocopherols and xanthophylls correlated positively with milk total fat content and correlated with percentages of milk LA and ALA while no associations were observed between carotenes and milk fatty acid content/composition.The uptake and secretion in mammary gland vary among different lipids component;4.Both maternal-cord plasma and breast milk ?-tocopherol existed mainly as the natural occurring RRR-?-tocopherol(~80%).Significant positive correlations were observed in maternal plasma and milk RRR%,suggesting priority transport of RRR in early life due to its essential functions.