Guanylin is a 15 amino acid peptide that is secreted by goblet cells in the colon. Guanylin acts as an agonist of the guanylyl cyclase receptor GC-C and regulates electrolyte and water transport in intestinal and renalepithelia.[2][3] Upon receptor binding, guanylin increases the intracellular concentration of cGMP, induces chloride secretion and decreases intestinal fluid absorption, ultimately causing diarrhoea.[4] The peptide stimulates the enzyme through the same receptor binding
region as the heat-stable enterotoxins.[3]
Researches have found that a loss in guanylin expression can lead to colorectal cancer due to guanylyl cyclase C's function as an intestinal tumor suppressor.[5] When guanylin expression was measured on over 250 colon cancer patients, more than 85% of patients had a loss of guanylin expression in cancerous tissue samples by 100-1000 times when compared to the same patients's nearby healthy colon tissue.[5] Another study done on genetically engineered mice found that mice on a high calorie diet had reduced guanylin expression in the colon.[6] This loss of expression then resulted in guanylyl cyclase C inhibition and the formation of tumors, therefore linking diet-induced obesity with colorectal cancer. [6]
^ abcMarx UC, Klodt J, Meyer M, Gerlach H, Rösch P, Forssmann WG, Adermann K (September 1998). "One peptide, two topologies: structure and interconversion dynamics of human uroguanylin isomers". The Journal of Peptide Research. 52 (3): 229–40. doi:10.1111/j.1399-3011.1998.tb01480.x. PMID9774236.
