Milk lipids are an important source of infant nutrition, providing 40% of calories to human infants. Interference with lipid synthesis and/or secretion in mammary epithelial cells (MECs) leads to abnormalities in lactation and impaired neonatal growth. Milk lipid secretion is a tightly regulated, luminal epithelial cell specific, process, requiring synthesis, packaging and transport of triglyceride and cholesterol ester containing droplets (cytoplasmic lipid droplets - CLDs) to the apical plasma membrane where they are secreted by a unique membrane envelopment mechanism. The long-term objective of this study is to elucidate the molecular mechanisms underlying the formation, transport and secretion of CLDs by mammary epithelial cells. We hypothesize that adipophilin (ADPH), a prominent CLD surface associated protein, is required for both formation and secretion of CLDs and thus integrates lipid synthesis with lipid secretion in the lactating mammary gland. The hypothesis that ADPH is required for CLD formation and secretion in mammary epithelial cells will be tested in mice lacking the ADPH gene and in transgenic mice in which perilipin-A has displaced ADPH. Pup growth rate, lipid content of milk and CLD formation, size and subcellullar localization will be examined in tissues of ADPH-null and perilipin transgenic animals to establish the effects of ADPH deletion on mammary function, CLD metabolism and milk lipid secretion. Adenoviral vectors will be used to deliver variants of ADPH and mutants of its functional domains to mammary epithelial cells of ADPH-null mice to determine in what molecular forms its replacement rescues defects induced by the absence of the ADPH gene. Proteomic analysis of isolated mammary CLDs from ADPH-null and perilipin transgenic animals will be used to establish effects of these proteins on the general protein composition of CLDs and to identify potential alternative mediators of CLD formation and secretion. ADPH is a member of the PAT family of CLD associated proteins that are thought to be important regulators of triglyceride storage and metabolism in many mammalian cell types. The mammary epithelial cell, because it can be manipulated by both transgenic and adenoviral technology, offers the opportunity to understand structure-function relations applicable to lipid storage in many cells and tissues. ? ? ? ? ?

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
1R01HD045965-01A1
Application #
6822982
Study Section
Reproductive Endocrinology Study Section (REN)
Program Officer
Grave, Gilman D
Project Start
2004-08-06
Project End
2008-07-31
Budget Start
2004-08-06
Budget End
2005-07-31
Support Year
1
Fiscal Year
2004
Total Cost
$320,177
Indirect Cost
Name
University of Colorado Denver
Department
Obstetrics & Gynecology
Type
Schools of Medicine
DUNS #
041096314
City
Aurora
State
CO
Country
United States
Zip Code
80045
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Libby, Andrew E; Bales, Elise; Orlicky, David J et al. (2016) Perilipin-2 Deletion Impairs Hepatic Lipid Accumulation by Interfering with Sterol Regulatory Element-binding Protein (SREBP) Activation and Altering the Hepatic Lipidome. J Biol Chem 291:24231-24246
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Wahlig, Jessica L; Bales, Elise S; Jackman, Matthew R et al. (2012) Impact of high-fat diet and obesity on energy balance and fuel utilization during the metabolic challenge of lactation. Obesity (Silver Spring) 20:65-75

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