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Abstract

The transition from pregnancy to lactation is a critical event in the survival of the newborn since all the nutrient requirements of the infant are provided by milk. While milk contains numerous components, including proteins, that aid in maintaining the health of the infant, lactose and milk fat represent the critical energy providing elements of milk. Much of the research to date on mammary epithelial differentiation has focused upon expression of milk protein genes, providing a somewhat distorted view of alveolar differentiation and secretory activation. While expression of milk protein genes increases during pregnancy and at secretory activation, the genes whose expression is more tightly regulated at this transition are those that regulate lipid biosynthesis. The sterol regulatory element binding protein (SREBP) family of transcription factors is recognized as regulating fatty acid and cholesterol biosynthesis. We propose that SREBP1 is a critical regulator of secretory activation with regard to lipid biosynthesis, in a manner that responds to diet, and that the serine/threonine protein kinase Akt influences this process, resulting in a highly efficient lipid synthetic organ that is able to support the nutritional needs of the newborn.

Biology of breast cancer during pregnancy using genomic profiling

“…In order to evaluate the potential role of pregnancy in the normal breast tissue, we investigated the expression of genes or gene sets that were found to be differentially expressed between the pregnant and non-pregnant groups on a publically available murine data set derived from the normal breast of pregnant mice (GEO ID: GSE8191; Anderson et al 2007). In the murine model, the breast tissue samples were obtained on days 1, 3, 7, 12, and 17 of pregnancy and also on day 19 (post-partum).…”

MicroRNA-26a/b and their host genes synergistically regulate triacylglycerol synthesis by targeting theINSIG1gene

“…11 Milk fat is one of the main components in goat dairy products, and provides an important source of nutrition for humans. 2 Ninety-eight percent of goat milk fat is composed of triacylglycerol (TAG), 25 which is mainly stored in cytoplasmic lipid droplets and secreted from mammary epithelial cells (MEC). 16 Milk fat quality and production have recently become important concerns in the dairy industry.…”

Insights into the role of connexins in mammary gland morphogenesis and function

“…During early pregnancy, prolactin and progesterone are the main drivers of extensive branching of ducts and alveolar bud formation that continues during late pregnancy and into lactation (Macias & Hinck 2012). As a result, the volume ratio of epithelial cells to adipocytes increases as the epithelial compartment expands and adipocytes undergo delipidation (Anderson et al 2007). In parallel to the morphogenic changes in the pregnant mammary gland, luminal epithelial cells undergo differentiation as many genes involved in milk synthesis begin to be expressed during midpregnancy (Anderson et al 2007).…”

“…As a result, the volume ratio of epithelial cells to adipocytes increases as the epithelial compartment expands and adipocytes undergo delipidation (Anderson et al 2007). In parallel to the morphogenic changes in the pregnant mammary gland, luminal epithelial cells undergo differentiation as many genes involved in milk synthesis begin to be expressed during midpregnancy (Anderson et al 2007). With the withdrawal of progesterone at parturition, the gland undergoes secretory activation as the mammary gland is set up as an exocrine gland to perform its main function to produce, secrete, and deliver milk (Pang & Hartmann 2007).…”