Effect of Adropin on Pancreas Exocrine Function in a Rat Model: A Preliminary Study

SIMPLE SUMMARY: Adropin plays an important role in the regulation of energy homeostasis and metabolism. It enhances glucose tolerance, improves insulin resistance, ameliorates lipid metabolism, and has antihyperlipidemic activity. It has previously been detected in various organs, including the pancreas. Our aim was to investigate whether adropin affects pancreas exocrine secretion. The influence of different doses of adropin was tested in basal and stimulated conditions (CCK-8 and vagal stimulation). In addition, the effect of adropin has been studied under vagotomy and capsaicin deafferentation conditions. Our results indicate that adropin inhibits pancreas exocrine secretion both in the basal and stimulated conditions, whereas vagotomy and deafferentation abolish the pancreas responses to adropin. Based on the obtained results, it can be assumed that the effect of adropin on the pancreas is related to an indirect vagal mechanism. Nevertheless, this hypothesis requires further verification. ABSTRACT: The aim was to investigate the potential effect of adropin (ADR) on pancreatic–biliary juice (PBJ) secretion (volume, protein content, trypsin activity) in a rat model. The animals were divided into control and five experimental groups: adropin, CCK-8 (CCK-8 stimulation), capsaicin (capsaicin deactivation of afferents), vagotomy (vagotomy procedure), and vagal stimulation (vagal nerve stimulation). The experiment consisted of four phases, during which vehicle (0.9% NaCl) and three ADR boluses (5, 10, and 20 µg/kg BW) were administered i.v. every 30 min. PBJ samples were collected from each rat at 15 min intervals after boluses. Exogenous ADR failed to affect the pancreatic responses after vagotomy and the capsaicin pretreatment and reduced the PBJ volume, protein outputs, and trypsin activity in the adropin, CCK-8, and vagal stimulation groups in a dose-dependent manner. In all these groups, volume of PBJ was reduced only by the highest dose of ADR (p < 0.001 for adropin group and p < 0.01 for CCK-8 and vagal stimulation groups), and the protein outputs were reduced by the administration of ADR 10 µg/kg BW (adropin and CCK-8 groups, p < 0.01 in both cases) and 20 µg/kg BW (p < 0.001 for adropin and CCK-8 groups, p < 0.01 for vagal stimulation group). The 10 µg/kg BW dose of ADR reduced the trypsin output in the CCK-8 group (p < 0.01), and the highest ADR dose reduced the trypsin output in the CCK-8 (p < 0.001) and vagal stimulation (p < 0.01) groups. In conclusion, adropin in the analyzed doses exhibits the negative feedback pathway. This mechanism seems to participate in the regulation of pancreatic juice secretion via an indirect vagal mechanism.