THE GUT-BRAIN PEPTIDE CYCLO(HIS-PRO) IS SECRETED IN A PULSATILE FASHION IN FASTING HUMANS

Histidyl-proline diketopiperazine (CHP) is a cyclic dipeptide that is found in many animal tissues, most notably brain and gut. It has been found to have a variety of biologic actions and has been postulated to play a role in appetitive behavior and energy metabolism. This study was conducted in order to characterize the secretory pattern of CHP du ring a 24 h fast. Four subjects (2 obese and 2 lean) were studied duri ng the latter 24 h of a 36 h fast. Blood was sampled every 10-15 min a nd assayed for CHP concentration using a specific radioimmunoassay. An alysis revealed that circulating CHP oscillates in humans and that diu rnal variation occurred but only in the obese subjects.