Effect of reproductive states on lipid mobilization and linoleic acid metabolism in mammary glands |
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Authors: | Gautam K Bandyopadhyay Le-Young Lee Raphael C Guzman Satyabrata Nandi |
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Affiliation: | (1) Cancer Research Laboratory, Department of Molecular and Cell Biology, University of California, 491 Life Sciences Addition, 94720 Berkeley, California |
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Abstract: | Effects of pregnancy and lactation on lipid metabolism in mouse mammary fat pads and nonmammary adipose tissues have been
studied. In order to address the question whether the influence of hormonal milieu on lipid metabolism in mammary epithelial
cells during pregnancy and lactation is the same as in fat cells, we have studied the mobilization of lipids and metabolism
of fatty acids in the intact mammary glands, parenchyma-free mammary fat pads and in the perimetrial fat tissues of virgin,
pregnant and lactating mice. Compared to parenchyma-free mammary fat pads, the perimetrial adipose tissues accumulated 5-fold
higher levels of triglycerides during pregnancy. Mammary fat cells maintained overall lipid levels during pregnancy and lactation
(16–20 μg/fat pad). In contrast, lactation depleted total lipid stores from 108 ± 5 to 24 ± 4.5 μg/fat pad in perimetrial
fat pads. Results of comparative analysis of fatty acid composition of mammary fat pads, with and without epithelial tissue,
from virgin and lactating mice showed stimulation of 18∶2ω6 metabolism leading to 130% increase in the ratio 20∶4ω6 to 18∶2ω6
in the epithelial compartment. Pregnancy and lactation resulted in the elevation of 20∶4ω6 levels probably due to a 4-fold
increase in Δ5 desaturase activity and a decrease in oxidative degradation of 18∶2ω6. These results suggest that, unlike other
adipose tissues, the metabolic pathways in mammary fat cells are not dedicated to sequestration and accumulation of dietary
lipids during pregnancy. Lactation favors mammary epithelial cell-stimulated production of precursors of eicosanoids which
are known to have agonist-like effect on mammary epithelial cells. |
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