Diabetes Mellitus Reduces The Expression Of Betatrophin In Pancreatic Islet Cells

Betatrophin, a peptide hormone expressed in liver and fat cells, has been reported to increase the rate of pancreatic β‐cell proliferation and β‐cell mass expansion. The present study determines whether the pancreatic content of betatrophin is reduced after the onset of diabetes mellitus (DM). DM was induced in adult male rats by a single intraperitoneal injection of streptozotocin (STZ) at a dose of 60 mg/kg body weight. Pancreatic tissue fragments were fixed overnight in freshly prepared Zamboni's fixative. The fixed tissue samples were embedded in paraffin wax. Sections of 6 μm thickness were cut on a microtome and processed for immunofluorescence. For immunoelectron microscopy, pancreatic tissue fragments (2 mm3) were fixed in McDowell's fixative and embedded in resin. Nickel grids with sections of pancreatic tissue were rinsed in 0.01 M sodium citrate buffer at 90°C for 5 minutes, cooled and jet‐washed with de‐ionized water. The sections were later immunostained using antibodies against either a combination betatrophin/insulin or betatrophin/glucagon. DM caused a significant reduction in the expression of betratrophin in pancreatic islet cells. Moreover, betatrophin was localized with insulin and glucagon in pancreatic islet cells. Betatrophin was found mainly in the secretory granules of insulin‐ and glucagon‐producing cells. These findings suggest a possible role of betatrophin in pancreatic endocrine function. Support or Funding Information This study was supported by a research grant from the UAEU