The age-associated decline in the intestinal uptake of glucose is not accompanied by changes in the mRNA or protein abundance of SGLT1

Abstract

Studies performed using human and animal models offer conflicting results regarding the effect of age on nutrient absorption. The objectives of this study were to determine (1) the effects of aging on the in vitro uptake of glucose in rats; and (2) the molecular mechanisms of these age-associated changes. Male Fischer 344 rats aged 1, 9 and 24 months were fed a standard laboratory diet (PMI # 5001). The uptake of 14C-labelled D-glucose was determined in vitro using the intestinal sheet method. Northern blotting, Western blotting and immunohistochemistry were used to determine the effects of age on the BBM sodium-dependent glucose transporter, SGLT1, and the BLM Na+K(+)-ATPase. When expressed on the basis of intestinal weight, mucosal weight or surface area, there was a reduction in glucose uptake in the 24-month-old animals. SGLT1, GLUT2 and Na+K(+)-ATPase mRNA and protein abundance did not parallel the changes seen in glucose uptake. These results indicate that (1) age reduces in vitro intestinal glucose uptake in the rat; and (2) this age-associated decline in glucose uptake was not explained by alterations in SGLT1, GLUT2 or Na+K(+)-ATPase.