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Trans ‐18∶1 isomers in rat milk fat as effective biomarkers for the determination of individual isomeric trans ‐18∶1 acids in the dams' diet
Author(s) -
Wolff Robert L.
Publication year - 2003
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-003-1172-z
Subject(s) - vaccenic acid , chemistry , elaidic acid , trans fat , lactation , sunflower oil , food science , clinical chemistry , breast milk , rapeseed , milk fat , stereochemistry , linseed oil , biochemistry , cholesterol , linoleic acid , biology , saturated fat , fatty acid , pregnancy , conjugated linoleic acid , genetics
Female rats were fed a diet containing by weight 10% partially hydrogenated sunflower oil, 2% sunflower oil, and 1% rapeseed oil during gestation and lactation. The trans ‐18∶1 isomer profile of the fat supplement was (in % of total trans 18∶1 acids in the fat supplement): Δ4, 0.5; Δ5, 1.0;Δ6–Δ8, 18∶0; Δ9 (elaidic), 13.5; Δ10, 22.2;Δ11 (vaccenic), 16.0; Δ12, 11.3; Δ13–Δ14, 12.8; Δ15, 2.5; and Δ16, 2.2 (total trans 18∶1 acids in the fat supplement: 40.6%). The cis 18∶1 isomer profile was (in % of total cis ‐18∶1 isomers):Δ6, Δ8, 2.1; Δ9 (oleics), 70.9; Δ10, 6.1; Δ11, 8.3; Δ12, 4.0; Δ13, 2.8; Δ14, 4.6, and Δ15, 1.2 (total cis ‐18∶1 acids in the fat supplement: 32.6%). Suckling rats from four litters were sacrificed at day 17 or 18 after birth, and their stomach content (milk) was analyzed. The trans ‐18∶1 isomer profile of milk was (relative proportions, in % of total): Δ4, 0.3; Δ5, 1.1; Δ6–Δ8, 16.8; Δ9, 15.3; Δ10, 22.0; Δ11, 16.7; Δ12, 11.8; Δ13–14, 11.8; Δ15, 2.5, and Δ16, 1.9 (total trans 18∶1 acids in milk: %). That of cis ‐18∶1 isomers was (proportions in % relative to total cis ‐18∶1 isomers): Δ6–Δ8, 4.7; Δ9, 72.5; Δ10, 4.0; Δ11, 8.0; Δ12, 7.1; Δ13, 1.9; Δ14, 1.0, and Δ15, 0.7 (total cis ‐18∶1 acids in milk: %). These results demonstrate that all isomeric acids, independent of the geometry and the position of the ethylenic bond, are incorporated into milk lipids. With regard to trans ‐18∶1 isomers, the distribution profile in milk is identical to that in the dams' diet, i.e., there is no discrimination against any positional isomer between their ingestiona nd their deposition into milk lipids. As a consequence, this study indicates that the trans ‐18∶1 isomer profile of milk reflects that in the dams' diet and supports our earlier hypothesis that the profile of trans ‐18∶1 isomers in milk can be used to deduce the relative contribution of ruminant fats and partially hydrogenated oils in the diet ot the total intake of trans ‐18∶1 isomers. On the other hand, the cis ‐18∶1 isomer profile in milk shows significant differences when compared to that in the dams' diet. Surprisingly, there are no major differences for the cis ‐Δ9 (oleic) and the cis ‐Δ11 (asclepic) isomers, which can be synthesized by the mother. However, there seems to be a significant positive selectivity for the group cis ‐Δ6–Δ8, and for the cis ‐Δ12 isomer, whereas a negative selectivity occurs for the Δ10 and Δ13 to Δ15 cis isomers.