THE CASE STUDY OF RESISTIN IN SHEEP: CAN DIET INFLUENCE THE MOLECULE’S LOCALIZATION IN THE ENDOCRINE PANCREAS?

Resistin (RETN), a recently discovered adipokine, is a cysteine-rich and secretory protein produced by adipocytes [1]. The RETN has been detected in several tissues, including human and lab animals' pancreas, wherein impairs glucose tolerance and insulin action and causes insulin resistance [2]. This study aimed to evaluate the presence and expression of RETN in the pancreas of 15 adult female sheep reared on Apennine pastures, which show a decrease in their nutritional value due to the increasing stress from summer drought [3]. The sheep were divided into 3 groups according to the diet they were subjected to maximum pasture flowering (MxF) group, maximum pasture dryness (MxD) group, and experimental (Exp) group which received a feed supplementation in addition to the MxD group feeding. As a preliminary analysis, immunohistochemistry (IHC) and immunofluorescence (IF) techniques were performed on formalin-fixed and paraffin-embedded sections of the pancreas to detect the RETN presence and to evaluate the co-expression of RETN with both glucagon (GCG)- and insulin (INS)-producing cells. Mouse monoclonal anti-RETN, rabbit polyclonal anti-GCG, and anti-INS, as primary antibodies, were used to carry out both IHC and IF. The RETN was observed in the endocrine cells and colocalized with both GCG-secreting alpha cells and INS-secreting beta cells, showing a wide distribution throughout the pancreatic islets. No differences in distribution and signal intensity of RETN, GCG, and INS were observed among the three groups of animals fed on different diets. These data show that RETN protein is produced by the cells of pancreatic islets, including the alpha and beta cells. Nevertheless, further investigations are needed to determine the overall role of pancreatic RETN. The IHC investigation did not reveal any differences related to diet. The RT-qPCR evaluation of RETN, GCG, and INS expression will further characterize the influence of different diets on pancreatic islet functionality.