Structural and Functional Abnormalities in the Islets Isolated From Type 2 Diabetic Subjects

TLDR

Type 2 diabetes involves both insulin resistance and pancreatic islet abnormalities, but it is unclear whether the islet defects are primary or secondary to insulin dysfunction. The study isolated and compared islets from 14 type 2 diabetic donors and 14 matched normal donors to assess β‑cell mass and function. Islets from diabetic donors showed impaired glucose‑stimulated insulin secretion in perifusion assays. Diabetic islets had reduced mass, were smaller with more α‑cells, and failed to normalize blood glucose in transplanted mice, demonstrating direct islet abnormalities that may drive type 2 diabetes.

Abstract

Type 2 diabetic subjects manifest both disordered insulin action and abnormalities in their pancreatic islet cells. Whether the latter represents a primary defect or is a consequence of the former is unknown. To examine the β-cell mass and function of islets from type 2 diabetic patients directly, we isolated islets from pancreata of type 2 diabetic cadaveric donors (n = 14) and compared them with islets from normal donors (n = 14) matched for age, BMI, and cold ischemia time. The total recovered islet mass from type 2 diabetic pancreata was significantly less than that from nondiabetic control subjects (256,260 islet equivalents [2,588 IEq/g pancreas] versus 597,569 islet equivalents [6,037 IEq/g pancreas]). Type 2 diabetic islets were also noted to be smaller on average, and histologically, islets from diabetic patients contained a higher proportion of glucagon-producing α-cells. In vitro study of islet function from diabetic patients revealed an abnormal glucose-stimulated insulin release response in perifusion assays. In addition, in comparison with normal islets, an equivalent number of type 2 diabetic islets failed to reverse hyperglycemia when transplanted to immunodeficient diabetic mice. These results provide direct evidence for abnormalities in the islets of type 2 diabetic patients that may contribute to the pathogenesis of the disease.