In neonatal rats, intestinal maturation is characterized by delayed expression of the fructose transporter GLUT5 until weaning. Distal intestine segments in jejunoileal atresia (JIA) are not exposed to amniotic fluid-containing carbohydrates. In human babies, the influence of intestinal maturation and obstruction on mucosal monosaccharide transporter expression was investigated.

Samples were collected from 10 infants who had small intestinal atresia surgery and 17 adults who had gastroduodenoscopy and/or ileocolonoscopy. The transporters SGLT1, GLUT1, GLUT2, GLUT5, and GLUT7 were assessed in newborn samples proximal and distal to the atresia, as well as adult duodenum, ileum, and colon. Immunofluorescence was used to examine protein expression and localization. 


Although monosaccharide transporter mRNA expression did not change substantially between newborn and adult samples, the luminal fructose transporter GLUT5 protein was missing in 0- to 4-day-old newborns but expressed in adults. The mRNA expression of the five monosaccharide transporters examined remained constant, distant, and proximal to the JIA. Similarly, immunofluorescence labeling revealed that the luminal sodium-dependent glucose transporter SGLT1 and the basolateral GLUT2 were expressed proximal and distal to JIA. With the exception of the glucose transporter GLUT1, which exhibited the greatest levels of expression in the colon, all studied hexose transporters showed the highest levels of expression in the duodenum, the lowest levels in the ileum, and the lowest levels in the colon.

Human infants lack the protein expression of the small intestine fructose transporter GLUT5, and small intestinal atresia has no effect on the expression of hexose transporters.