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Obestatin, acylated and total ghrelin concentrations in the perinatal rat pancreas
Jean-Pierre Chanoine1, Alfred C K Wong, Vicente Barrios
1Endocrinology and Diabetes Unit, British Columbia's Children's Hospital, University of British Columbia, Vancouver, Canada. jchanoine@cw.bc.ca
Insights
Ghrelin and obestatin peptides are present in the developing rat pancreas and may influence insulin secretion. Acylated ghrelin levels increase significantly after birth, suggesting a role in neonatal development.
Area of Science:
- Endocrinology
- Developmental Biology
- Gastroenterology
Background:
- Ghrelin and obestatin are peptides derived from the preproghrelin gene.
- These peptides are found in the fetal rat pancreas, along with growth hormone secretagogue receptor mRNA.
- Acylated ghrelin is known to inhibit insulin secretion.
Purpose of the Study:
- To investigate the developmental changes (ontogeny) of ghrelin and obestatin in rat plasma and tissues.
- To understand the relationship between ghrelin, obestatin, and insulin during perinatal development.
Main Methods:
- Measurement of obestatin, acylated ghrelin, and total ghrelin concentrations.
- Analysis of plasma, pancreas, and stomach samples from fetal and neonatal rats at various time points (F20, PN1, PN6, PN12, PN21).
Main Results:
- Obestatin concentrations were consistently lower than total ghrelin.
- Plasma total ghrelin decreased post-birth, while acylated ghrelin increased significantly.
- Pancreatic acylated ghrelin showed a substantial increase from fetal to neonatal stages.
- Positive correlations were observed between ghrelin/obestatin and insulin concentrations in the pancreas.
Conclusions:
- Ghrelin and obestatin are present in the perinatal rat pancreas.
- These peptides may play a role in regulating insulin secretion during early development.
Background:
Ghrelin and obestatin are encoded by the preproghrelin gene and originate from posttranslational processing of the preproghrelin peptide. The fetal rat pancreas contains acylated and desacylated ghrelin peptides, as well as growth hormone secretagogue receptor -1a mRNA. Acylated ghrelin inhibits insulin secretion. We investigated the plasma and tissue ontogeny of ghrelin and obestatin in the rat.
Methods:
We measured obestatin and acylated and total ghrelin concentrations in plasma, pancreas and stomach from rat fetuses (F20) and neonates at postnatal day (PN) 1, 6, 12 and 21).
Results:
Overall, obestatin concentrations were markedly lower than total ghrelin concentrations. In plasma, total ghrelin concentrations decreased abruptly after birth (p < 0.05), contrasting with a 3 times increase in the concentration of acylated ghrelin between F20 and PN1 (p < 0.05). In pancreas, total ghrelin and obestatin concentrations decreased progressively from PN1 to PN21 but acylated ghrelin concentrations increased 6-7 times from F20 (18 [6] pg/ml) to PN6 (122 [59] pg/ml). The percent of acylated ghrelin increased from 1.8 (0.6) at F20 to 39.7 (13.0) % of total ghrelin immunoreactivity at PN12 (p < 0.05). There were significant positive correlations between postnatal obestatin, acylated or total ghrelin and insulin concentrations in the pancreas (all p < 0.02, r(2) > 0.21) and between postnatal total ghrelin and obestatin (in pancreas, r(2) = 0.37) or acylated ghrelin (in stomach, r(2) = 0.27) (p < 0.001).
Conclusion:
Ghrelin and obestatin are present in the perinatal pancreas where they could potentially affect insulin secretion.
