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HORMONES AND SIGNALING

Exendin-4, but not dipeptidyl peptidase IV inhibition, increases small intestinal mass in GK rats

Departments of ¹Medical Physiology, ²Medical Anatomy, and ³Pharmacology, University of Copenhagen, Copenhagen, Denmark

Submitted 2 October 2006 ; accepted in final form 12 April 2007

Long-term treatment with dipeptidyl peptidase IV inhibitors (DPPIV-I) or glucagon-like peptide (GLP)-1 analogs may potentially affect intestinal growth by down- or upregulating the intestinotrophic hormone GLP-2. This study compared the intestinotrophic effects of 12-wk administration of vehicle, exendin-4 (Ex-4; 5 nmol/kg bid sc), or DPPIV-I (NN-7201, 10 mg/kg qd orally) in GK rats. Some animals were observed additionally for 9 wk after the end of treatment. Both treatments lowered glycated hemoglobin A1c at wk 12 vs. control (Ex-4, –0.8%; DPPIV-I, –0.4%). Body weight was reduced by Ex-4 compared with control (361 ± 4 vs. 399 ± 5 g; P < 0.001) because of reduced food intake, whereas neither parameter was affected by DPPIV-I. Linear bone growth was unaffected by either treatment. After treatment end, food intake in Ex-4 animals increased, and, by wk 21, body weight was identical in all groups. The small intestine of Ex-4-treated animals was larger at wk 12 compared with control (length, 135.6 ± 1.6 vs. 124.5 ± 2.3 cm, P < 0.001; absolute weight, 8.4 ± 0.2 vs. 6.4 ± 0.4 g, P < 0.001), being most pronounced proximally, where the absolute cross-sectional area related to body weight increased by 24% because of increased mucosal thickness. These effects were reversible, and 9 wk after the end of treatment, no differences between Ex-4 and control were apparent. Plasma GLP-2 concentrations were unaltered by either treatment, and Ex-4 had no agonistic or antagonistic effects on the transfected GLP-2 receptor. DPPIV-I had no intestinal effects. In conclusion, the continued presence of Ex-4 is necessary to maintain weight loss in GK rats. Effective antihyperglycemic treatment with Ex-4 increases intestinal mass reversibly, whereas DPPIV-I lacks intestinal effects.

glucagon-like peptide-1; glucagon-like peptide-2; glucagon-like peptide-1 receptor; glucagon-like peptide-2 receptor; intestinotrophic