Effect of glucagon-like peptide-2 (GLP-2) on diurnal SGLT1 expression

Glucagon-like peptide 2 (GLP-2) is a 33-amino acid gut peptide that leads to villus hyperplasia and altered gene expression. We examined the effect of chronically administered GLP-2 on diurnal gene expression rhythms using the Na+/glucose cotransporter 1 (SGLT1) as the index. Animals were treated with [Gly(2)]GLP-2 (twice daily; 1 mug/g body weight) or vehicle (control) for 10 days. Rats were killed at either 3 hr or 9 hr after light onset (ZT3 and ZT9, respectively), an interval during which SGLT1 expression exhibits a robust induction. SGLT1 mRNA expression was assessed by Northern blotting and in situ hybridization. SGLT I protein was examined by immunofluorescence and Western blotting. Tissues from GLP-2-treated rats had increased villus height, crypt depth, and proliferation index (P<0.05). GLP-2 administration did not alter the diurnal increase in mRNA levels of SGLT1, GLUT2, or GLUT5. However, in GLP-2-treated rats, the SGLT1 protein amount increased at both ZT3 and ZT9. Moreover, SGLT1 was preferentially localized to the apical membranes in this group. GLP-2 does not adversely affect the diurnal expression rhythm of SGLT I and appears to increase membrane expression of the protein. These biological actions of GLP-2 may contribute to its therapeutic value in intestinal diseases.