Effects of ghrelin treatment to promote proliferation of pancreatic islet in BB rats
Maria Gloria Baena, Isabel Maria Lomas-Romero, Gonzalo Pérez-Arana, Manuel Blandino-Rosano, Carmen Segundo, Manuel Aguilar-Diosdado & Alfonso M Lechuga-Sancho
Aims: BB rats develop diabetes as young adults by an autoimmune mechanism. Ghrelin is a peptidic hormone synthesized mainly in the oxintic cells of the gastric mucosae in adults. During intrauterine life however, this peptide is synthesized mainly at the pancreas. Ghrelin exerts proliferative and survival promoting effects in different cell types. We investigated the effect of ghrelin treatment in a diabetes autoimmune animal model to analyze death rate and cellular proliferation of the β-cells in the pancreatic islets.
Methods: BB rats received ghrelin subcutaneously once a day at 10 ng/kg, since postnatal week 4. Non treated animals received the same volume of buffer. Animals were daily weighed and their diuresis and intake monitored. Glycaemia was measured weekly. Animals were killed at postnatal weeks 5, 7, 9 and 11. Pancreata were dissected and immediatelly frozen in liquid nitrogen and conserved at −80 °C until sectioned. Pancreata were sliced in eight micron-thick slices using a cryostat. Infiltrates were quantified using hemotoxylineosin staining. β-Cell proliferation and apoptosis rate were assessed by BrdU and TUNEL inmunuhistochemistry. Fifty islets were counted per animal.
Results: No animal became diabetic before week 10. On week 10, three out of the four BB non treated rats presented diabetic onset (75%) and none of the five BB rats receiving ghrelin did (P<0.008). No different effects on weight gain, diuresis and glycaemia until diabetes onset was found. Ghrelin treatment increased the number of replicating cells from week 9 and 10. We found no difference in the inflammatory infiltration of islets and the rate of apoptosis.
Conclusions: These findings indicate that ghrelin promote proliferation of β-cell in BB rats. This suggests ghrelin plays a role in the control of islet cell survival. However, this effect dies not seem to be mediated by modulation of the inmune response.