Luminal polyamines upregulate transmural glucose transport in the rat small intestine

Polyamines, which are contained in many foods, play an important role in the growth and differentiation of the enterocyte, but their role in glucose transport is unclear. Using isolated rat small intestine and a nonrecirculating perfusion system, we studied the effect of luminal polyamines on glucose uptake and on the concentration of sodium-glucose transporter 1 (SGLT1) and glucose transporter 5 (GLUT5) proteins.

In the control group, 300mg glucose solution was administered through the jejunum, and the glucose concentration in the portal vein was measured for 15 min. In treatment groups, various concentrations of polyamine (putrescine [Put] or spermine [Spm]) were administered simultaneously with the glucose. At the end of the perfusion period, the amount of SGLT1, GLUT5, and aminopeptidase N (APN) in the brush border membrane was subjected to Western blot analysis.

Glucose concentration in the portal vein increased after the simultaneous administration of glucose and polyamines, and the area under the curve (AUC) after the 15-min perfusion was enhandced to 188%, 196%, 132%, and 192% by 0.5mM Spm, 4mM Spm, 1 mM Put, and 8 mM Put, respectively. The brush border membrane concentration of SGLT1 protein 15 min after polyamine administration was also enhanced in all treatment groups, and it correlated with the AUC. The concentration of GLUT5, on the other hand, was reduced by 4mM Spm, and the concentration of APN was not affected by polyamine administration.

Luminal polyamines increase glucose absorption in the small intestine via the rapid enhancement of SGLT1 protein in the brush border membrane.