Endothelial Na+-D-glucose cotransporter: no role in insulin-mediated glucose uptake.
A recent report indicates that the Na+-D-glucose cotransporter SGLT1 is present in capillaries of skeletal muscle and is required for insulin-mediated glucose uptake in myocytes. This result is based on the complete inhibition of insulin-mediated muscle glucose uptake by phlorizin, an inhibitor of SGLT1. Using the pump-perfused rat hind limb, we measured glucose uptake, lactate efflux, and radioactive 2-deoxyglucose uptake into individual muscles with saline (control), phlorizin, insulin, and insulin plus phlorizin, as well as with saline and insulin using normal and low Na+ perfusion buffer. Insulin-mediated glucose uptake was not inhibited after correction for phlorizin interference in the glucose assay. Lactate efflux and 2-deoxyglucose uptake by individual muscles were unaffected by phlorizin. Low Na+ buffer did not affect insulin-mediated glucose uptake, lactate efflux, or 2-deoxyglucose uptake. We conclude that endothelial SGLT1 exerts no barrier for glucose delivery to myocytes.
Kolka
C M
CM
Dept of Biochemistry, Medical School, University of Tasmania, Hobart, Australia. ckolka@utas.edu.au
Rattigan
S
S
Richards
S M
SM
Barrett
E J
EJ
Clark
M G
MG
D000818:Animals; D004730:Endothelium, Vascular / Q000502:physiology*; D005947:Glucose / Q000378:metabolism*; D006614:Hindlimb / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D010695:Phlorhizin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D051269:Sodium-Glucose Transporter 1 / Q000502:physiology*
D007328:Insulin; C495676:Slc5a1 protein, rat; D051269:Sodium-Glucose Transporter 1; D010695:Phlorhizin; D005947:Glucose