Abstract
BackgroundLactose, as the primary osmotic component in milk, is the major determinant of milk volume. Glucose is the primary precursor of lactose. However, the effect of glucose on lactose synthesis in dairy cow mammary glands and the mechanism governing this process are poorly understood.ResultsHere we showed that glucose has the ability to induce lactose synthesis in dairy cow mammary epithelial cells, as well as increase cell viability and proliferation. A concentration of 12 mM glucose was the optimum concentration to induce cell growth and lactose synthesis in cultured dairy cow mammary epithelial cells. In vitro, 12 mM glucose enhanced lactose content, along with the expression of genes involved in glucose transportation and the lactose biosynthesis pathway, including GLUT1, SLC35A2, SLC35B1, HK2, β4GalT-I, and AKT1. In addition, we found that AKT1 knockdown inhibited cell growth and lactose synthesis as well as expression of GLUT1, SLC35A2, SLC35B1, HK2, and β4GalT-I.ConclusionsGlucose induces cell growth and lactose synthesis in dairy cow mammary epithelial cells. Protein kinase B alpha acts as a regulator of metabolism in dairy cow mammary gland to mediate the effects of glucose on lactose synthesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0704-x) contains supplementary material, which is available to authorized users.
Highlights
Lactose, as the primary osmotic component in milk, is the major determinant of milk volume
Effect of glucose on lactose synthesis in dairy cow mammary epithelial cells Glucose is the primary precursor of lactose in lactating mammary glands
Protein kinase B alpha and its active form, pAKT1, were upregulated in mammary epithelial cells cultured in DMEM with 12 mM glucose compared with the control (P < 0.05; Fig. 3e, f ). These results strongly suggested that glucose induced lactose synthesis in mammary epithelial cells by upregulating glucose transporter 1 (GLUT1), solute carrier family 35 member A2 (SLC35A2), solute carrier family 35 member B1 (SLC35B1), hexokinase 2 (HK2), β4GalT-I, and AKT1
Summary
As the primary osmotic component in milk, is the major determinant of milk volume. Glucose is the primary precursor of lactose. The effect of glucose on lactose synthesis in dairy cow mammary glands and the mechanism governing this process are poorly understood. The basic function of the lactating mammary gland is to produce milk, providing nutrients for growth and development of the offspring. The main constituents of bovine milk are lactose, proteins, and lipids [1]. Lactose is the major carbohydrate of milk. It plays a primary role in milk production because it represents the main osmotic constituent in milk and draws water into the mammary epithelial cells [2]. Lactose is synthesized from free glucose and uridine diphosphate (UDP)-galactose.
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