Expression of Na+/glucose co-transporter 1 (SGLT1) in the intestine of piglets weaned to different concentrations of dietary carbohydrate.
Na+/glucose co-transporter 1 (SGLT1) transports dietary sugars from the lumen of the intestine into enterocytes. Regulation of this protein is essential for the provision of glucose to the body and, thus, is important for maintenance of glucose homeostasis. We have assessed expression of SGLT1 at mRNA, protein and functional levels in the intestinal tissue of 28 d old piglets weaned onto isoenergetic diets with differing concentrations of digestible carbohydrate (CHO). We show that expression of SGLT1 remains constant when piglets are fed up to 40 % CHO-containing diets. However, there is a significant increase in SGLT1 expression when the CHO content of the diet is>50 %. Morphometric analyses indicate that the increased expression is not due to a trophic effect. It has been proposed that in rat intestine, in response to a high-CHO diet, GLUT2 (the classical basolateral membrane monosaccharide transporter) is translocated to the luminal membrane of enterocytes to absorb excess dietary glucose. We show, using immunohistochemistry and Western blotting with antibodies raised to amino acids in different epitopes of GLUT2, that under all dietary conditions, low to high CHO, GLUT2 is expressed on the basolateral membrane of pig enterocytes. Furthermore, functional studies indicate that there is no uptake of 2-deoxy-D-glucopyranoside, a specific substrate of Na+-independent glucose transporters into brush-border membrane vesicles isolated from the intestines of piglets either maintained on low- or high-CHO diets. Thus, SGLT1 is the major route for absorption of dietary sugars across the luminal membrane of swine enterocytes.
Moran
Andrew W
AW
Epithelial Function and Development Group, Department of Veterinary Preclinical Sciences, University of Liverpool, Liverpool, UK.
Al-Rammahi
Miran A
MA
Arora
Daleep K
DK
Batchelor
Daniel J
DJ
Coulter
Erin A
EA
Ionescu
Catherine
C
Bravo
David
D
Shirazi-Beechey
Soraya P
SP
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D019422:Dietary Sucrose / Q000378:metabolism*; D020895:Enterocytes / Q000378:metabolism*; D000939:Epitopes; D005260:Female; D005947:Glucose / Q000378:metabolism*; D051273:Glucose Transporter Type 2 / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D008871:Microvilli / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051269:Sodium-Glucose Transporter 1 / Q000235:genetics / Q000378:metabolism*; D014886:Weaning
D004040:Dietary Carbohydrates; D019422:Dietary Sucrose; D000939:Epitopes; D051273:Glucose Transporter Type 2; D012333:RNA, Messenger; D051269:Sodium-Glucose Transporter 1; D012313:RNA; D005947:Glucose