Diabetes Mellitus Influences the Pattern of Distribution of Irisin in Pancreatic Islet Cells

Abstract

Irisin is a newly discovered myokine, which enhances the turnover of white adipose cells into brown fat cells. Irisin is derived from FNDC5, a membrane‐bound protein. Moreover, irisin has been shown to play an important role in energy regulation especially in muscle cells. Although, irisin has been detected in many organs including the exocrine pancreas, liver, testes and sebaceous gland, a precise localization of this polypeptide in pancreatic islet cells has not been undertaken. Immunohistochemistry was used to determine the pattern of distribution of irisin in streptozotocin‐induced (60 mg/Kg body weight) diabetes in rats. Image J® software was used to quantify the number of irisin‐immunoreactive cells in diabetic and non‐diabetic rat pancreas. Our study shows that irisin is present in a large number of pancreatic beta cells where it co‐localizes with insulin. In contrast, irisin does not co‐localize with glucagon in normal rat pancreas. However, this pattern of distribution changes after the onset of diabetes mellitus (DM). DM is characterized by increased number of glucagon immunopositive cells. The newly formed glucagon‐positive cells now contain irisin as well. The reason why irisin co‐localizes with glucagon in diabetic rat pancreas and not in non‐diabetic rats is unclear. It is possible that in diabetic rats, insulin, the natural inhibitor of glucagon has been removed paving way for glucagon expression in pancreatic beta cells devoid of insulin. The presence of irisin in insulin secreting beta cells suggests that the beneficial effect of irisin on glucose metabolism could indeed be via the endocrine pancreas.Support or Funding InformationUnited Arab Emirates University