Objective: To investigate the association of gastric emptying with ghrelin, obestatin and GHSR, GPR-39 in hypothalamus of diabetic rats.
Methods: Sixty Wistar rats were randomly divided into three groups: a normal control group (NC, n = 20), a diabetes mellitus group (DM, n = 20) induced by intraperitoneal injection of streptozotocin (STZ) and an insulin treated group (INS, n = 20). After two and six weeks of STZ injection, gastric emptying was measured by intragastric administration of phenol red, ghrelin and obestatin in hypothalamus measured by ELISA (enzyme-linked immunosorbent assay) and GHSR and GPR-39 by RT-PCR (reverse transcription-polymerase chain reaction).
Results: After two weeks of STZ injection, gastric emptying (%) (74 +/- 8, 40 +/- 5), ghrelin level(ng/g) (52 +/- 9, 51 +/- 7) and ratio of ghrelin/obestatin (3.8 +/- 1.0, 2.8 +/- 1.0) increased significantly in DM and INS groups compared to those in NC group [32% +/- 7%, (39 +/- 11) ng/g, 2.1 +/- 0.8, all P < 0.05]. Obestatin level(ng/g) (14.2 +/- 2.0) of hypothesis decreased significantly in DM group as compared to those in NC group (21.7 +/- 4.7) while GHSR/beta-actin increased significantly (1.26 +/- 0.46 vs 0.77 +/- 0.21, P < 0.05). Gastric emptying was positively correlated with ghrelin, ghrelin/obestatin and GHSR/beta-actin of hypothalamus (r = 0.49; r = 0.63; r = 0.73; P < 0.01). But there was a negative correlation with obestatin of hypothalamus (r = -0.74, P < 0.01). After six weeks of STZ injection, gastric emptying (78.97% +/- 8.13% vs 44.06% +/- 5.06%) increased significantly in DM and INS groups as compared to those in NC group (35.06% +/- 3.91%, P < 0.01). Gastric emptying was positively correlated with ghrelin/obestatin of hypothalamus (r = 0.40, P < 0.05). There was no detection of GPR-39 in hypothalamus.
Conclusion: The rapid gastric emptying may be due to the rising levels of ghrelin and GHSR in hypothalamus during early hyperglycemia. And the duration of hyperglycemia is affected by the rising ratio of ghrelin/obestatin.