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Journal of animal physiology and animal nutrition

Glucose transport and milk secretion during manipulated plasma insulin and glucose concentrations and during LPS-induced mastitis in dairy cows.


PMID 25319117

Abstract

In dairy cows, glucose is essential as energy source and substrate for milk constituents. The objective of this study was to investigate effects of long-term manipulated glucose and insulin concentrations in combination with a LPS-induced mastitis on mRNA abundance of glucose transporters and factors involved in milk composition. Focusing on direct effects of insulin and glucose without influence of periparturient endocrine adaptations, 18 dairy cows (28xa0±xa06xa0weeks of lactation) were randomly assigned to one of three infusion treatments for 56xa0h (six animals each). Treatments included a hyperinsulinemic hypoglycaemic clamp (HypoG), a hyperinsulinemic euglycaemic clamp (EuG) and a control group (NaCl). After 48xa0h of infusions, an intramammary challenge with LPS from E. coli was performed and infusions continued for additional 8xa0h. Mammary gland biopsies were taken before, at 48 (before LPS challenge) and at 56xa0h (after LPS challenge) of infusion, and mRNA abundance of genes involved in mammary gland metabolism was measured by RT-qPCR. During the 48xa0h of infusions, mRNA abundance of glucose transporters GLUT1, 3, 4, 8, 12, SGLT1, 2) was not affected in HypoG, while they were downregulated in EuG. The mRNA abundance of alpha-lactalbumin, insulin-induced gene 1, κ-casein and acetyl-CoA carboxylase was downregulated in HypoG, but not affected in EuG. Contrary during the intramammary LPS challenge, most of the glucose transporters were downregulated in NaCl and HypoG, but not in EuG. The mRNA abundance of glucose transporters in the mammary gland seems not to be affected by a shortage of glucose, while enzymes and milk constituents directly depending on glucose as a substrate are immediately downregulated. During LPS-induced mastitis in combination with hypoglycaemia, mammary gland metabolism was more aligned to save glucose for the immune system compared to a situation without limited glucose availability during EuG.

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