Background:Diurnal rhythms of transporter expression are well-described in the jejunum. We hypothesized that similar rhythmicity exists in the ileum, and compared jejunal and ileal expression of Sglt1, Glut2, Glut5 and Asbt.
Methods:Rats acclimatized to a 12 hour photoperiod were killed at ZT3, ZT9, ZT15 and ZT21 (Lights-on is ZT0; n=6 per time) mucosal scrapings were collected from jejunum and ileum. Sglt1, Glut2, Glut5 and ASBT mRNA levels were measured using quantitative PCR and analyzed by ANOVA.
Results:All 3 hexose transporters exhibited diurnal rhythmicity in jejunum and ileum. Sglt1 mRNA was highest at ZT9 in jejunum and ZT15 in ileum (both p<0.01 vs. ZT3 and ZT21; Fig 1). Glut2 and Glut5 mRNAs were significantly higher at ZT9 compared to ZT3 (p<0.05). Rhythmicity was not observed for ASBT mRNA in either region.
Discussion:Sglt1 expression exhibits rhythmicity in the ileum similar to the jejunum with a lower magnitude and slight delay. Rhythmic expression of Glut2 and Glut5 also persists in the ileum. The absence of Asbt rhythmicity is consistent with the constant presence of luminal bile acids. Elucidating the mechanisms underlying these variations will enhance efforts to modulate intestinal absorption.