Adverse Effects of Coumestrol and Genistein on Mammary Morphogenesis and Future Milk Production Ability of Mammary Epithelial Cells.

Isoflavones are a class of flavonoids present in legumes and are called phytoestrogens because of their estrogen-like activity. Endogenous estrogen is well known to regulate mammary gland morphogenesis during pregnancy. Each isoflavone also has different physiological activities. However, it is difficult to investigate the direct effect of each isoflavone in mammary morphogenesis in vivo because isoflavones are metabolized into different isoflavones by enteric bacteria. In this study, investigated are the direct influences of coumestrol, daidzein, and genistein on mammary structure development and future milk production ability of mammary epithelial cells (MECs) using in vitro culture models. Mouse MECs are cultured in Matrigel with basic fibroblast growth factor and epidermal growth factor to induce ductal branching and alveolar formation, respectively. Coumestrol and genistein inhibit ductal branching and alveolar formation by affecting the proliferation and migration of MECs with the induction of apoptosis. Daidzein hardly influences mammary structure development. Furthermore, pretreatment with coumestrol adversely affects the induction of milk production ability of MECs. These results suggest that each isoflavone differentially influences mammary morphogenesis and future milk production by affecting MEC behaviors. These results also suggest that the culture models are effective to study mammary epithelial morphogenesis in vitro.

IL-1ß directly inhibits milk lipid production in lactating mammary epithelial cells concurrently with enlargement of cytoplasmic lipid droplets.

Mammary epithelial cells (MECs) in lactating mammary glands produce milk lipid, which provides a large percentage of calories and bioactive lipids for appropriate infant growth. However, secreted milk lipid is often reduced concurrently with increases in IL-1ß, IL-6, and TNF-α in mammary glands with mastitis. In this study, we investigated whether those cytokines directly influenced lipid production and secretion. A lactating MEC culture model with high lipid production ability was prepared by culture with oleic acid. TNF-α, IL-1ß, and IL-6 differentially affected lipid production and secretion in lactating MECs. In particular, IL-1ß treatment significantly reduced amounts of secreted triglycerides by 97% compared with the control concurrently with enlargement of cytoplasmic lipid droplets in MECs. IL-1ß also decreased mRNA expression of Fabp3 and Srebp1 and the amount of aquaporin 3, GLUT-1 and adipophilin in the milk lipid production pathway. Furthermore, IL-1ß inactivated STAT5 and glucocorticoid signaling to induce milk production in MECs, whereas STAT3 and NFκB signaling was activated. IL-1ß induced mRNA expression of IL-6 and TNF-α in MECs. Therefore, we suggest that IL-1ß is a key inhibitor of lipid production and secretion in lactating MECs.