ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2008) 16 P512

No feedback inhibition of obestatin during acylated ghrelin infusion in humans

Barbara Lucatello, David H. St-Pierre, Fabio Settanni, Ilaria Olivetti, Andrea Benso, Riccarda Granata, Ezio Ghigo & Fabio Broglio

University of Turin, Turin, Italy.

Background: Obestatin is a 27 aa peptide derived from the ghrelin gene. Obestatin was first described to exert anorexigenic effects by decreasing gastric motility in rodent models, however these results have been debated and there is presently only small information regarding its activity and its regulation in humans. Furthermore, its interactions with acylated ghrelin (AG), derived from the same gene, have not been evaluated. Therefore, in these preliminary data, we sought to evaluate obestatin levels in normal subjects submitted to a 2 h infusion with 1 μg/kg per h AG or isotonic saline.

Methods: Three normal subjects were included in the study. An isotonic saline infusion was maintained for 1 h and then, either AG (1 μg/kg per h) or isotonic saline was continuously administrated iv for 2 h. Blood samples were collected at times −60, −30, 0, 30, 60, 90 and 120 min. For each treatment, infusion, peak, nadir and AUC obestatin values were evaluated. Glycemia and insulin levels were evaluated for each timepoints.

Results: Baseline circulating obestatin concentrations were respectively 246±102 ng/ml and 242±111 ng/ml for the 2 treatment groups (isotonic saline and AG infusions). Furthermore, obestatin levels were not significantly modulated by the administration of either isotonic saline (mean value=267±56 ng/ml) or AG (mean value=270±81 ng/ml). These results suggest that both observed insulin and obestatin circulating concentrations could be correlated (r=−0.60; P=0.59).

Conclusion: This preliminary study suggests that obestatin levels are not regulated by a feedback mechanism during an AG infusion in normal subjects. Meanwhile, the possibility of an association between obestatin and insulin concentrations could be investigated in further studies.

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