Glucose transporter gene expression in bovine mammary gland.

Abstract

Transport of glucose across the plasma membrane of mammary epithelial cells is believed to be a passive process of facilitated diffusion mediated by facilitative glucose transporter(s). This article presents three lines of evidence that indicate the expression of sodium/glucose cotransporter (SGLT1) in the mammary gland of lactating and nonlactating cows. First, transcripts of SGLT1 mRNA ranging in size from 1.5 to 5.2 kb were detected in polyadenylated RNA preparations of mammary glands of lactating and nonlactating cows. Second, SGLT1 cotransporter protein was also detected in plasma membrane preparations of mammary glands of lactating cows. Third, partial amino acid sequence deduced from the reverse transcriptase-PCR fragment of SGLT1 from bovine mammary glands was similar to the sequence reported for ovine SGLT1. We conclude that mammary gland expression of SGLT1 mRNA and protein suggests that an active glucose transport system may be involved in glucose transport and metabolism in the mammary gland of dairy cows. However, the physiological significance of the expression of SGLT1 in mammary gland remains unknown.

Functional Analyse of GLUT1 and GLUT12 in Glucose Uptake in Goat Mammary Gland Epithelial Cells

“…GLUT1 is a receptor of HTLV infection in CD4+T cells [37], and HIV-1 infection in CD4+T cells is abrogated in the absence of surface GLUT1 [40]. Recent studies [7], [22], [41], [42] have found that GLUT1 is most abundantly expressed in mammary glands and that the levels increase during pregnancy and peak during lactation, results that may be related to the abundant synthesis of proteins and lactose in breast tissue. In this study, using breast epithelial cells, the data for glucose uptake in the GT1-GMGE cells confirmed that the cloned GLUT1 possesses glucose transport activity, a result that corresponded to the high expression of GLUT1 mRNA in the GT1-GMGE cells.…”

“…GLUT1 has a ubiquitous distribution in tissues and culture cells [5]–[7] and is considered to be the primary transporter responsible for basal glucose uptake. GLUT1 expression is detected abundantly in the mammary gland [8] and increases during pregnancy and lactation.…”

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

“…Considering the importance of glucose in lactating ruminants, the mechanisms underlying the regulation of glucose uptake into the mammary gland and subsequent utilization are subject of this research. The effects of manipulated glucose concentrations on mammary glucose transporters were mostly investigated in vitro (Zhao et al., ; Xiao and Cant, ), while in vivo studies focused on changes in gene expressions of glucose transporters during the lactation–gestation cycle in lactating dairy cows (Zhao and Keating, ,b; Mattmiller et al., ). Altered plasma glucose concentrations do not only affect glucose transporters in the mammary gland, but have also an impact on genes involved in the synthesis of milk constituents (Liu et al., ).…”

Associations among milk production traits and glycosylated haemoglobin in dairy cattle; importance of lactose synthesis potential

“…However; a lactating mammary gland cannot synthesize glucose from other precursors due to the absence of glucose-6-phosphatase (Threadgold and Kuhn 1979) and so is dependent on the blood supply for its glucose requirement. Mammary glucose uptake, which is performed by both active and passive transport processes (Zhao et al 1999(Zhao et al , 2005, is independent of the concentration of glucose and insulin in the arterial blood during lactation. It has also been suggested that the blood glucose concentration affects the rate of synthesis of milk lactose, hence milk volume by osmotic association (Kronfeld 1982).…”