Introduction: Several cholecystokinin (CCK) forms have been detected in plasma, but most studies on food intake investigated the effects of CCK-8 only. Recently, it has been demonstrated that CCK-58 is the only endocrine-active form of CCK in rats.
Methods: CCK-58 was synthesized with a peptide synthesizer using FMOC chemistry and CCK-58 effects on food intake were compared to CCK-8 in rats.
Results: Both CCK-58 and CCK-8 inhibited food intake in a dose-dependent manner and were equally potent at 30 min. CCK-58 showed a prolonged inhibition of food intake compared to CCK8 at the higher dose tested (7 nmol/kg), inhibiting food intake also at 60 min, and cumulative food intake was inhibited for up to 210 min by CCK-58.
Conclusions: CCK-58 has the same potency in inhibiting food intake as CCK-8 in rats, but inhibits food intake longer. This might be due to its tertiary structure resulting in a delayed plasma degradation or a prolonged binding at the CCK receptor. As CCK-58 is the major CCK form in the gut wall and possibly in the circulating blood in humans, the effects of CCK on food intake might have been underestimated in the past.