Insulitis and aging: Immune cell dynamics in Langerhans islets.

Area of Science:

• Immunology
• Endocrinology
• Gerontology

Background:

• Aging is linked to increased type-2-diabetes risk, involving impaired glucose tolerance and insulin secretion.
• Immune cell activity, inflammation, and fibrosis are implicated in age-related diabetes, but their role in healthy aging islets is unclear.
• Understanding immune cell dynamics in aging pancreatic islets is crucial for beta-cell health and glucose metabolism regulation.

Purpose of the Study:

• To investigate immune cell composition, accumulation, and fibrosis in pancreatic islets of young versus aged male C57BL/6J mice.
• To determine the influence of age-related immune cell changes on glucose metabolism and beta-cell function.
• To explore the relationship between insulitis, fibrosis, and metabolic compensation in healthy aging.

Main Methods:

• Comparative analysis of pancreatic islets from young and aged male C57BL/6J mice.
• Assessment of immune cell populations (leukocytes, macrophages, T-cells) and fibrosis.
• Evaluation of beta-cell mass, insulin secretion capacity, and glucose tolerance.

Main Results:

• Insulitis (inflammation of islets) was observed in aged mice without immediate diabetic phenotype.
• Aged islets showed increased leukocytes with a shift towards macrophages and T-cells.
• Aged mice exhibited increased beta-cell mass and partially enhanced insulin secretion, leading to improved glucose tolerance despite insulitis and increased fibrosis.

Conclusions:

• Immune cell subtypes change with age in pancreatic islets.
• Non-pathological immune cell accumulation, particularly macrophages and T-cells, may support beta-cell function and regulate glucose metabolism via cytokines.
• Compensatory mechanisms, including increased beta-cell mass and insulin secretion, help maintain glucose homeostasis in healthy aging despite insulitis and fibrosis.