Covariation of plasma ghrelin and motilin in irritable bowel syndrome

We have previously shown that ghrelin is mainly localized to the stomach but also occurs, together with the prokinetic hormone motilin, in endocrine cells in the proximal small intestine. This study explored ghrelin and motilin concentrations in plasma in relation to gastrointestinal motility and whether plasma ghrelin is changed in patients with irritable bowel syndrome (IBS). Nine patients with severe IBS and 10 healthy subjects underwent stationary antro-duodeni-jejunal manometry; blood was sampled during similar motility phases in the two groups. The motility phases were monitored and blood samples were collected during fasting and after food intake. Plasma was analyzed for two forms of ghrelin (octanylated and desoctanylated) as well as for motilin. In IBS patients circulating motilin levels covaried with total ghrelin levels (r = 0.90; p < 0.004), octanylated ghrelin (r = 0.77; p < 0.02) and desoctanylated ghrelin (r = 0.69; p < 0.04). No such correlations were seen in the control group. Octanylated ghrelin comprised 35.3 ± 3.9% (mean ± SEM) of the total circulating ghrelin in the IBS patients compared to 40.4 ± 4.5% (mean ± SEM) in the control group (NS). Ghrelin covaried with motilin in plasma in IBS but not in plasma from healthy subjects. This suggests the two peptides act together in IBS.