Hexose transporter expression in rat small intestine: effect of diet on diurnal variations.
In rodents, a number of intestinal digestive and absorptive processes demonstrate a diurnal pattern of activity. To investigate if the jejunal hexose transporters are regulated in such a diurnal fashion, the levels for the glucose and fructose transporter mRNA and proteins were determined at 6-h intervals over a 24-h control fed period. SGLT-1, GLUT-2, and GLUT-5 mRNA levels increased between two- and eightfold before the onset of peak feeding. GLUT-5 protein levels also varied in a diurnal fashion but were out of phase with the observed changes in GLUT-5 mRNA levels. In contrast, GLUT-2 protein levels remained relatively constant during the control fed 24-h period. The effect of dietary manipulations on the observed diurnal variation was also investigated. After only 3 h of feeding a 60% fructose-enriched diet, the levels of GLUT-5 mRNA and protein were significantly elevated. GLUT-5 mRNA and protein levels remained elevated relative to the level of control diet-fed animals over the ensuing 24 h and during the 7th day of fructose feeding. Exposure to elevated levels of fructose had no significant effect on the diurnal pattern of GLUT-2 and SGLT-1 mRNA. In contrast, GLUT-2 protein was rapidly downregulated during the length of the fructose feeding study. In conclusion, the data demonstrate a normal daily variation in the level of hexose transporter expression that can be rapidly modulated by diet.
Corpe
C P
CP
Department of Medicine, University of Chicago, Illinois 60637, USA.
Burant
C F
CF
D000818:Animals; D002940:Circadian Rhythm; D004032:Diet; D005632:Fructose / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology; D051273:Glucose Transporter Type 2; D051296:Glucose Transporter Type 5; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051269:Sodium-Glucose Transporter 1
D051273:Glucose Transporter Type 2; D051296:Glucose Transporter Type 5; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C495676:Slc5a1 protein, rat; D051269:Sodium-Glucose Transporter 1; D005632:Fructose; D005947:Glucose