Context: The global prevalence of diabetes mellitus, and in particular type 2 diabetes mellitus is increasing at an alarming rate. Risk factors for development of diabetes include obesity and advancing age.
Objectives: The distribution of insulin, glucagon, somatostatin and pancreatic polypeptide in the pancreatic islets has been investigated in young and elderly type 2 Zucker diabetic fatty (ZDF) rats and age-matched Zucker lean (ZL) controls.
Methods: Experiments were performed in male animals aged either 9-13 weeks or 30-34 weeks. Immunohistochemistry was used to label insulin, glucagon, somatostatin and pancreatic polypeptide in islet cells.
Results: The percentage of insulin-positive cells was unaltered in young but decreased in elderly ZDF (35.5 ± 2.5%) rats compared to ZL controls (57.9 ± 1.8%). The percentage of glucagon-positive cells was increased in young ZDF (58.7 ± 3.4%) compared to ZL controls (23.4 ± 2.1%). However, in elderly rats the percentage of glucagon-positive cells declined in ZDF rats and was no longer different from ZL controls. The percentage of somatostatin-positive cells was unaltered in young and elderly ZDF rats compared to ZL controls. The percentage of pancreatic polypeptide-positive cells was unaltered in young but increased in elderly ZDF (22.0 ± 2.5%) rats compared to ZL controls (13.8 ± 1.8%).
Conclusions: The distribution of pancreatic hormones is altered to varying extents in the ZDF rat and during the normal aging process.