Expression and Regulation of Facilitative Glucose Transporters in Equine Insulin-Sensitive Tissue: From Physiology to Pathology

Table 1

Summary of the main location and function of facilitative glucose transporter family [7, 8, 156].

Protein	Major sites of expression	Proposed function/major substrate	Major species studied
GLUT1	Many cell types (e.g., erythrocytes, brain); fetal tissues	Basal glucose uptake; transport across blood-tissue barriers	Rodents, humans, horses, cows, dogs, pigs
GLUT2	Kidney, small intestine, liver, pancreatic islets, brain	High-capacity low-affinity facilitated glucose and fructose transporter	Rodents, humans, horses, cows
GLUT3	Brain (neurons) and testis	High-affinity facilitated glucose transporter; neuronal transport	Rodents, humans, cows, dogs, pigs
GLUT4	Striated muscle, fat, heart	High-affinity facilitated glucose transporter; insulin-regulated transport; linked to IR/diabetes	Rodents, humans, horses, cows, dogs, pigs
GLUT5	Small intestine, kidney, striated muscle, fat, testis	Facilitated fructose transporter	Rodents, humans, horses, cows, dogs, pigs
GLUT6	Leukocytes, brain, spleen	Facilitated glucose transporter
GLUT7	Small intestine, colon, testis	Transport of glucose and fructose
GLUT8	Testis, brain, blastocyst, striated muscle, fat, liver, spleen, lung	Facilitated glucose transporter widely expressed; neuronal transport; insulin-responsive transport in blastocyst	Rodents, humans, cows, horses
GLUT9	Liver, kidney, small intestine	Facilitated urate (glucose) transporter	Rodents, humans
GLUT10	Striated muscle, lung, liver, pancreas
GLUT11	Striated muscle	Muscle-specific; facilitated glucose/fructose transporter	Rodents, humans
GLUT12	Striated muscle, fat, prostate, mammary gland	A second insulin-responsive facilitated GLUT?	Rodents, humans, cows, horses
HMIT	Brain, fat	H^+/myo-inositol cotransporter
GLUT14	Testis	Orphan transporter