Effects of glucose availability on expression of the key genes involved in synthesis of milk fat, lactose and glucose metabolism in bovine mammary epithelial cells

• Published in: PloS one 2013-06, Vol.8 (6), p.e66092-e66092
• Main Authors: Liu, Hongyun, Zhao, Ke, Liu, Jianxin
• Format: Article
• Language: English
• Subjects: Acetyl-CoA carboxylase; Acetyl-CoA Carboxylase - genetics; Acetyl-CoA Carboxylase - metabolism; Agriculture; Analysis; Animal lactation; Animals; Availability; Biology; Biosynthetic Pathways; Biotechnology; Cattle; Cells, Cultured; Cow's milk; Dairy cattle; Dehydrogenases; Diacylglycerol O-Acyltransferase - genetics; Diacylglycerol O-Acyltransferase - metabolism; Education; Energy balance; Enzymes; Epithelial cells; Epithelial Cells - enzymology; Fat metabolism; Fatty Acid Synthase, Type I - genetics; Fatty Acid Synthase, Type I - metabolism; Fatty acid synthesis; Fatty acids; Fatty-acid synthase; Female; Gene Expression; Gene Expression Regulation; Genes; Glucose; Glucose - metabolism; Glucose 6 phosphate dehydrogenase; Glucosephosphate dehydrogenase; Glucosephosphate Dehydrogenase - genetics; Glucosephosphate Dehydrogenase - metabolism; Glycerol; Glycerol-3-Phosphate O-Acyltransferase - metabolism; Glycolysis; Kinases; Laboratories; Lactalbumin; Lactose; Lactose - biosynthesis; Lactose synthase; Lactose Synthase - genetics; Lactose Synthase - metabolism; Lipid Metabolism - genetics; Mammary gland; Mammary Glands, Animal - cytology; Membrane Potential, Mitochondrial; Metabolism; Milk; Milk - metabolism; Milk production; Milk proteins; Nutrition; Oils & fats; Osmoregulation; Pentose; Pentose phosphate pathway; Phosphates; Physiological aspects; Protein binding; Pyruvate kinase; Pyruvate Kinase - genetics; Pyruvate Kinase - metabolism; Pyruvic acid; RNA; RNA, Messenger - genetics; RNA, Messenger - metabolism; Rodents; Sterol regulatory element-binding protein; Synthesis; Veterinary Science
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0066092

As the main precursor for lactose synthesis, large amounts of glucose are required by lactating dairy cows. Milk yield greatly depends on mammary lactose synthesis due to its osmoregulatory property for mammary uptake of water. Thus, glucose availability to the mammary gland could be a potential regulator of milk production. In the present study, the effect of glucose availability on expression of the key genes involved in synthesis of milk fat, lactose and glucose metabolism in vitro was investigated. Bovine mammary epithelial cells (BMEC) were treated for 12 h with various concentrations of glucose (2.5, 5, 10 or 20 mmol/L). The higher concentrations of glucose (10-20 mmol/L) did not affect the mRNA expression of acetyl-CoA carboxylase, diacyl glycerol acyl transferase, glycerol-3 phosphate acyl transferase and α-lactalbumin, whereas fatty acid synthase, sterol regulatory element binding protein-1 and beta-1, 4-galactosyl transferase mRNA expression increased at 10 mmol/L and then decreased at 20 mmol/L. The content of lactose synthase increased with increasing concentration of glucose, with addition of highest value at 20 mmol/L of glucose. Moreover, the increased glucose concentration stimulated the activities of pyruvate kinase and glucose-6-phosphate dehydrogenase, and elevated the energy status of the BMEC. Therefore, it was deduced that after increasing glucose availability, the extra absorbed glucose was partitioned to entering the synthesis of milk fat and lactose by the regulation of the mRNA expression of key genes, promoting glucose metabolism by glycolysis and pentose phosphate pathway as well as energy status. These results indicated that the sufficient availability of glucose in BMEC may promote glucose metabolism, and affect the synthesis of milk composition.