Pituitary Pars Intermedia Dysfunction Down-regulates mRNA Abundance of Genes Encoding GLUT4 and Insulin Receptor in the Small Intestinal Mucosa of the Horse

Abstract

To test the hypothesis that hexose transporter transcripts are in lower abundance in the large compared with the small intestine of the horse, mRNA abundance of genes encoding for hexose transporters was quantified in small and large intestinal segments of the horse. Four adult horses were euthanized, and mucosal samples were taken from two segments of the small intestine (distal jejunum [DJ] and ileum [IL]) and three segments of the large intestine (cecum [CE], left ventral colon [LVC], and left dorsal colon [LDC]). Transcript abundance of candidate hexose transporter genes was determined using reverse transcription quantitative polymerase chain reaction. Primers for genes SLC2A1, SLC2A2, SLC2A5, and SLC5A1, encoding for the hexose transporter proteins GLUT1, GLUT2, GLUT5, and SGLT1, respectively, were designed using gene sequences from GenBank. The 2ΔΔCT method was used to compare mRNA abundance of candidate genes in the IL, CE, LVC, and LDC with that of the DJ. Relative to the DJ, mRNA abundance of GLUT1 was not different in the IL, CE, and LVC, and increased (P ≤ .05) in the LDC. GLUT2, GLUT5, and SGLT1 gene expression was not different in the IL, and decreased (P ≤ .01) in the CE, LVC, and LDC, relative to the DJ. The decrease in expression for the majority of the hexose transporter genes in the large intestine indicates that it has less capacity for glucose, galactose, or fructose absorption compared with the small intestine of the horse.