A glucagon-like peptide-1 (GLP-1) analog, liraglutide, has been reported to block inflammatory somatic pain. We hypothesized that liraglutide attenuates lipopolysaccharide (LPS)- and repeated water avoidance stress (WAS)-induced visceral hypersensitivity and tested the hypothesis in rats.
METHODS:
The threshold of the visceromotor response (VMR) induced by colonic balloon distention was measured to assess visceral sensation. Colonic permeability was determined in vivo by quantifying the absorbed Evans blue spectrophotometrically, which was instilled in the proximal colon for 15 min. The interleukin-6 (IL-6) level in colonic mucosa was also quantified using ELISA.
RESULTS:
Subcutaneously (s.c.) injected LPS (1 mg/kg) reduced the VMR threshold after 3 h. Liraglutide (300 µg/kg s.c.) at 15 h and 30 min before injecting LPS eliminated LPS-induced allodynia. It also blocked the allodynia induced by repeated WAS for 1 h for 3 consecutive days. Neither vagotomy nor naloxone altered the antinociceptive effect of liraglutide, but NG -nitro-L-arginine methyl ester, a nitric oxide (NO) synthesis inhibitor, blocked it. LPS increased colonic permeability and the IL-6 level, and the analog significantly inhibited these responses.
CONCLUSIONS:
This study suggests that liraglutide blocked LPS-induced visceral allodynia, which may be a NO-dependent response, and was probably mediated by inhibiting proinflammatory cytokine production and attenuating the increased gut permeability. Because the LPS-cytokine system is considered to contribute to altered visceral sensation in irritable bowel syndrome, these results indicate the possibility that liraglutide can be useful for treating this disease.
