Correlation between morphology and function in isolated islets of the Zucker rat

Area of Science:

• Endocrinology
• Metabolic Research
• Pancreatic Islet Biology

Background:

• Obesity in Zucker rats is characterized by hyperlipemia, hyperinsulinism, and insulin resistance.
• Pancreatic islets exhibit hyperplasia and hypertrophy in obese Zucker rats.
• Morphological heterogeneity of pancreatic islets may influence hormone secretion.

Purpose of the Study:

• To correlate pancreatic islet morphology (size) with insulin and glucagon secretion in Zucker rats.
• To investigate the relationship between islet size, protein content, and hormone release.
• To examine differences in islet function between lean and obese Zucker rats.

Main Methods:

• Isolation and perifusion of pancreatic islets from lean and obese Zucker rats.
• Categorization of islets into large (>0.45 mm) and small (<0.12 mm) based on diameter.
• Measurement of insulin and glucagon secretion in response to glucose, aminophylline, Br-cAMP, and arginine.

Main Results:

• Islets from obese rats secreted significantly more insulin than those from lean rats in response to glucose and aminophylline.
• Insulin release was directly proportional to islet size and protein content.
• Large islets were less efficient insulin releasers per unit volume compared to small islets.
• Glucagon release was stimulated by Br-cAMP and arginine in lean rats but blunted in large islets from obese rats.

Conclusions:

• Pancreatic islet size is a critical factor influencing both insulin and glucagon secretion in Zucker rats.
• Increased insulin secretion rates and blunted glucagon responses in obese Zucker rats are associated with islet size heterogeneity.
• Islet morphology plays a significant role in the pathophysiology of obesity-associated metabolic dysfunction.