Endogenous motilin, but not ghrelin plasma levels fluctuate in accordance with gastric phase III activity of the migrating motor complex in man

Background: Fluctuations in motilin plasma levels have been implicated in the control of the migrating motor complex (MMC). A plasma peak of motilin is present before a gastric phase III. Furthermore, not only exogenous administration of motilin but also ghrelin induces a gastric phase III in man. Aim of this study was to investigate the role of endogenous ghrelin in the regulation of the MMC.

Methods: Plasma samples for motilin and ghrelin were taken in between two consecutive phases III of either origin measured using high-resolution manometry.

Key results: The duration of 1 complete MMC cycle was on average 95 ± 12 min. Sixty percent of the first phases III and 40% of the second phases III had a gastric origin (p = 0.0574). Motilin (p < 0.05) plasma levels differed significantly between the phases of the MMC but total and octanoylated ghrelin did not. The percentage change in motilin during the MMC was dependent on the origin of phase III (p < 0.05). Motilin levels increased on average with 35 ± 10% right before a gastric phase III and with 3 ± 4% before a duodenal phase III (p < 0.05). The percentage change in total and octanoylated ghrelin plasma levels was not affected by the origin of phase III.

Conclusions & inferences: These results confirm the role of motilin but not of ghrelin as an endogenous physiological regulator of the MMC with a gastric phase III.