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Free oligosaccharides and glycosylation of bile salt-stimulated lipase in human milk
Linköping University, Department of Biomedicine and Surgery, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bile salt-stimulated lipase (BSSL) is a glycosylated protein present in milk at a concentration of 100-200 mg/L. It is an enzyme important for fat digestion in the newborn infant. The protein backbone contains one possible site for N-glyeosylation and several sites for 0-glyeosylation. The glycosylation of BSSL may be important for protection against proteolytic degradation and/or secretion of BSSL. The oligosaeeharides bound to BSSL may also, together with other protein-bound oligosacchatides and free oligosaecharides in milk, play an important role in the defense against pathogenic microorganisms. Human milk contains approximately 5-20 g/L of free milk oligosacchatides, and more than 100 different structures have been identified. There are individual differences in the content of milk oligosaeeharides depending on Lewis and seeretor status.

Milk samples were collected from healthy donors at different times during lactation. BSSL was purified from the milk of five donors. Structural characterization of BSSL glyeosylation was performed by high-performance anionexchange chromatography (HP AEC), Bio-Gel P-4 chromatography, lectin affinity chromatography, gas chromatography coupled to mass-spectrometry (MS) and mattix assisted laser desorption-ionization time-of-flight MS. Certain carbohydrate epitopes were detected by monoclonal antibodies and lectins. Some of the methods above were used in combination with ptior derivatization, desialylation or digestion with different exo- and endoglycosidases. Thirteen major free oligosaccharides were quantified in milk from five individuals. Free milk oligosacchatides were purified by P4-Gel chromatography and analyzed by HPAEC.

HP AEC coupled to pulsed amperometric detection is extensively used for analysis and quantification of oligosaccharides. Separation is achieved using highly alkaline conditions that lead to ionization of some of the hydroxyl groups, which can then interact with the anion-exchange matrix. The effect of colunm temperature was examined in a range of 13 to 40 oC. A large variation in retention times was found depending on small differences in colunm temperature. Moreover, individual oligosaccharides did not show the same temperature dependence. By use of different column temperatures, HP AEC could be optimized for analysis of milk oligosaccharides.

BSSL was found to contain approximately one N-linked and nine O-linked oligosaccharides. The 0-glycans were stmcturally heterogeneous and contained· fucose and/or sialic acid. Each 0-glycan contained an average of eight monosaccharide units. The major N-linked oligosaccharides on human BSSL were mono-sialylated biantennary complex type structures with or without one, two or three fucose residues.

Recombinant human BSSL expressed in CHO and C-127 cells were analyzed and found to be differently glycosylated than native BSSL. In contrast to native BSSL, recombinant BSSL did not contain fucose. On BSSL expressed in C-127 cells, the O-glycans were shorter and more extensively sialylated than O-glycans on native BSSL. The majority of N-linked oligosaccharides on recombinant BSSL had the same core structure (biantennary complex type) as native BSSL.

Glycosylation of BSSL changed during lactation. BSSL had a higher carbohydrate and sialic acid content in the first lactation month. There was also a shift from preferentially α2-6 to α2-3 linked sialic acid on the protein-bound oligosaccharides during lactation. This shift was also found for free sialylated milk oligosaccharides, and suggests a change in the activity of certain sialyltransferases during lactation.

A gradual increase in the expression of the fucosylated carbohydrate epitope Lewis x (Galß1-4[Fucal-3]GlcNAc-) was found on BSSL during the whole lactation period. This was reflected in a higher relative amount of fucosylated N-linked oligosaccharides present on BSSL later in lactation. A similar increase in fucosylation was indicated by analysis of free milk oligosaccharides. One of the major milk oligosaccharides, 3-fucosyllactose (3-FL), also increased in concentration during lactation. However, lacto-N-fucopentaose (LNFIII), the only free milk oligosaccharide containing the Lewis x epitope, showed a constant concentration. This finding does not exclude the possibility that the same fucosyltransferase is involved in the synthesis of Lewis x on BSSL, 3-FL and LNFIII. The precursor of LNFIII, lacto-N-neotetraose (LNnT) showed a marked decrease during lactation, which may explain the different pattem found for LNFIIl. The increase of 3-FL and Lewis x on BSSL was found for all individuals. The other free oligosaccharides studied decreased during lactation, except for lacto-N-fucopentaose li (LNFII), lacto-di-fucotetraose (LDFT) and 3-sialyllactose (3-SL), which showed constant concentrations.

Total fucosyltransferase activity decreased during lactation in milk from both secretors and non-secretors. The specific α1-3 fucosyl transferase activity toward lactose also decreased during lactation, which indicated that fucosyltransferase activity in milk does not reflect the activity in the mammary epithelial cells.

In conclusion, there are changes in glycosylation during lactation, which involves both protein-bound and free milk oligosaccharides. The different patterns for individual oligosaccharides indicate both down and up regulation of certain glycosyltransferases in the mammary gland during lactation. The importance of these changes for the infant's adaptation to the environment remains to be elucidated.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2001. , 80 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 657
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-25676Local ID: 10052ISBN: 91-7219-941-5 (print)OAI: oai:DiVA.org:liu-25676DiVA: diva2:246224
Public defence
2001-04-17, Berzeliussalen, Universitetssjukhuset, Linköping, 10:00 (Swedish)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-08-17Bibliographically approved
List of papers
1. Temperature effects in high-performance anion-exchange chromatography of oligosaccharides
Open this publication in new window or tab >>Temperature effects in high-performance anion-exchange chromatography of oligosaccharides
1998 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 814, no 1-2, 97-104 p.Article in journal (Refereed) Published
Abstract [en]

High-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection has been widely used for analysis of mono-, oligo- and polysaccharides. Many factors that affect separation of carbohydrates by HPAEC have been evaluated, however effect of temperature has not been carefully studied. In the present study, neutral and sialylated oligosaccharides from human milk and different types of N-linked oligosaccharides were analysed by HPAEC at temperatures ranging from 13 to 30°C. N-Acetyl neuraminic acid, galacturonic acid and stachyose were also analysed since they have been used as internal standards when analysing various oligosaccharides by HPAEC. All oligosaccharides showed decreased retention times with increased temperature. Even small differences in temperature (i.e. ±5°) resulted in considerable changes in retention times. In addition, individual oligosaccharides showed different relative changes in retention time with increased temperature. By changing the temperature, a switch in elution order of individual oligosaccharides were sometimes found. These results show that retention times relative to an internal standard cannot be used for oligosaccharide identification unless temperature is carefully controlled. Regulation of temperature is also a valuable tool in achieving optimal separation of oligosaccharides by HPAEC.

Keyword
Temperature effects, Oligosaccharides
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-79993 (URN)10.1016/S0021-9673(98)00381-1 (DOI)
Available from: 2012-08-17 Created: 2012-08-17 Last updated: 2017-12-07Bibliographically approved
2. Glycosylation of Bile-Salt-Stimulated Lipase from Human Milk: Comparison of Native and Recombinant Forms
Open this publication in new window or tab >>Glycosylation of Bile-Salt-Stimulated Lipase from Human Milk: Comparison of Native and Recombinant Forms
Show others...
1997 (English)In: Archives of Biochemistry and Biophysics, ISSN 0003-9861, E-ISSN 1096-0384, Vol. 344, no 1, 94-102 p.Article in journal (Refereed) Published
Abstract [en]

Bile-salt-stimulated lipase (BSSL) is an enzyme present in human milk. BSSL is important for fat digestion in infants. It contains one site for N-glycosylation and a serine/threonine-rich domain which is highly O-glycosylated. Both N- and O-linked sugar chains were studied on native BSSL from three donors and compared to the glycosylation of recombinant BSSL produced in Chinese hamster ovary or mouse fibroblast (C-127) cell lines. The carbohydrate composition of oligosaccharides was mapped using sugar and methylation analyses, enzyme-linked immunosorbant assay, and different separation techniques. Native BSSL was found to be highly glycosylated (19–26%). It contained a high amount of fucosylated oligosaccharides and expressed both Lewis a and Lewis b blood group antigens. None of the recombinant BSSL forms contained fucose. N-linked structures on native BSSL were identified as mainly mono- and disialylated biantennary complex type structures with or without fucose substitution. High-pH anion-exchange chromatography analysis indicated that the recombinant forms of BSSL contained similar types ofN-glycan structures differing mainly in their content of sialic acid and by the absence of fucose residues. Native BSSL contained predominantly large O-linked oligosaccharides. This was in contrast to the recombinant forms of BSSL which contained mainly short typeO-glycans with a high content of sialic acid. Interestingly, the estimated number of O-glycans attached to native BSSL was lower than that for the recombinant forms.

Keyword
bile-salt-stimulated lipase, glycosylation, high-pH anion-exchange chromatography, human milk, recombinant proteins
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-79994 (URN)10.1006/abbi.1997.0188 (DOI)
Available from: 2012-08-17 Created: 2012-08-17 Last updated: 2017-12-07Bibliographically approved
3. Changes in Glycosylation of Human Bile-Salt-Stimulated Lipase during Lactation
Open this publication in new window or tab >>Changes in Glycosylation of Human Bile-Salt-Stimulated Lipase during Lactation
Show others...
2000 (English)In: Archives of Biochemistry and Biophysics, ISSN 0003-9861, E-ISSN 1096-0384, Vol. 377, no 2, 246-254 p.Article in journal (Refereed) Published
Abstract [en]

Bile-salt-stimulated lipase (BSSL) is an enzyme in human milk, which is important for the fat digestion in the newborn infant. BSSL is highly glycosylated and includes one site for N-glycosylation and several sites for O-glycosylation. BSSL has previously been found to express Lewis a, Lewis b, and Lewis x carbohydrate antigens. In this study, glycosylation of BSSL was studied at different times during lactation. BSSL was purified from milk collected individually from four donors at several different times during the first 6 months of lactation. The BSSL glycans were characterized through monosaccharide analysis, high-pH anion-exchange chromatography, matrix-assisted laser desorption–ionization mass spectrometry, and ELISA. Both total carbohydrate content and relative amount of sialic acid were higher in BSSL from the first lactation month as compared to BSSL from milk collected later in lactation. BSSL from the first lactation month also showed a different composition of sialylated O-linked glycans and the N-linked oligosaccharides consisted of lower amounts of fucosylated structures compared to later in lactation. We also found a gradual increase in the expression of the carbohydrate epitope Lewis x on BSSL throughout the lactation period. This study shows that glycosylation of BSSL is dependent on blood group phenotype of the donor and changes substantially during the lactation period.

Keyword
bile-salt-stimulated lipase, glycosylation, Lewis x, human milk
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25198 (URN)10.1006/abbi.2000.1778 (DOI)9637 (Local ID)9637 (Archive number)9637 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13Bibliographically approved
4. Quantitative changes of fucosylated human milk oligosaccharides during lactation in comparison to milk fucosyltransferase activity
Open this publication in new window or tab >>Quantitative changes of fucosylated human milk oligosaccharides during lactation in comparison to milk fucosyltransferase activity
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Human milk contains 7-20 g/L of free oligosaccharides. The oligosaccharides show large variations in size and structure. It has been suggested that milk oligosaccharides can prevent pathogenic microorganisms from attaching to the gastrointestinal epithelium by blocking bacterial adhesins. However, the biological role of milk oligosaccharides is far from understood. In this study, the major fucosylated oligosaccharides in milk were followed during six to nine months of lactation. Individual oligosaccharides were separated and quantified by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The fucosylated oligosaccharides 2-fucosyl lactose, lacto-N-fucopentaose I and lacto-N-di-fucohexaose I showed decreasing concentrations in milk during lactation. The concentrations of lacto-difucotetraose, lacto-N-fucopentaose II and Ill remained constant, while 3-fucosyl lactose (3-FL) showed increasing concentrations during lactation. The increase of 3-FL was found for all individuals independent of secretor status, but did not correlate to milk fucosyltransferase activity when the product 3-FL was measured separately. Instead all individuals showed a decrease in fucosyltransferase activity during lactation, indicating that fucosyltransferase activity in milk does not reflect the biosynthetic activity in the mammary gland. This study shows that the composition of fucosylated oligosaccharides vary considerably during the first six months of lactation. This may reflect unique biological roles of certain oligosaccharides in the infant's adaptation to the environment.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-79998 (URN)
Available from: 2012-08-17 Created: 2012-08-17 Last updated: 2012-08-17Bibliographically approved
5. Changes in the relative amounts of α2-3 and α2-6 linked sialic acid on free and protein-bound milk oligosaccharides during lactation
Open this publication in new window or tab >>Changes in the relative amounts of α2-3 and α2-6 linked sialic acid on free and protein-bound milk oligosaccharides during lactation
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Human milk contains large amounts of oligosaccharides, both in free and protein-bound forms. Sialic acid is a common constituent of milk oligosaccharides and is present α2-3 or α2-6 linked to galactose, α2-6 to N-acetyl glucosamine or α2-6 to N-acetyl galactosamine. High-performance anionexchange chromatography with pulsed amperometric detection (HPAEC-PAD) was used to quantify four major sialylated milk oligosaccharides. The concentrations of the individual oligosaccharides were analyzed in milk from five donors, followed separately during six to nine months of lactation. The oligosaccharides containing sialic acid a2-6 linked to galactose ( 6-sialyl lactose and LSTc) decreased more than tenfold during lactation. In contrast, the concentration of 3-sialyl lactose (3-SL) containing sialic acid a2-3 linked to galactose remained constant during nine months of lactation. Disialyl lacto-Ntetraose (DSLNT) which contain sialic acid linked α2-3 to Gal and α2-6 to GlcNAc decreased approximately threefold during lactation. Lectin ELISA was used to analyze sialic acid on the secreted milk glycoprotein bile-salt-stimulated lipase (BSSL ). There was a gradual decrease in the binding of Sambucus Nigra lectin to BSSL, indicating decreased amount of α2-6 linked sialic acid during lactation. In contrast, binding of Maackia Amurensis lectin remained constant, indicating a constant expression of α2-3 linked sialic acid on BSSL during lactation. This suggests a shift from preferentially 6-linked to 3-linked sialic acid on free and protein-bound oligosaccharides during lactation. The shift may reflect changes in sialyltransferase activities and, on a higher level, changes in the population of mammary epithelial cells. This finding may be of importance for the development of a correct immune response to environmental challenges.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-80000 (URN)
Available from: 2012-08-17 Created: 2012-08-17 Last updated: 2012-08-17Bibliographically approved

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