Axonal dystrophy in experimental diabetic autonomic neuropathy

Area of Science:

• Neuroscience
• Diabetology
• Pathology

Background:

• Autonomic neuropathy is a common complication of diabetes mellitus.
• The gastrointestinal tract is frequently affected by diabetic autonomic neuropathy.
• Ultrastructural changes in peripheral nerves are key indicators of neuropathy.

Purpose of the Study:

• To characterize autonomic neuropathy in the alimentary tract of diabetic rats.
• To investigate the ultrastructural changes in unmyelinated axons in diabetic rats.
• To determine the temporal progression and potential patterns of diabetic autonomic neuropathy.

Main Methods:

• Utilized ultrastructural methods to examine nerve tissues.
• Induced chronic diabetes in inbred rat strains using streptozotocin.
• Analyzed ileal mesentery tissues from rats at various time points (3.5, 6, 9, and 12 months) post-diabetes induction.

Main Results:

• Observed markedly enlarged unmyelinated axons in the ileal mesentery of diabetic rats.
• Identified diverse subcellular organelles within these enlarged axons, resembling those in axonal dystrophies.
• Found axonal alterations increased in frequency with diabetes duration (6-12 months) but were absent at 3.5 months.
• Noted a proximo-distal gradient in lesion frequency, indicative of distal axonopathy.
• Associated dystrophic axons with regenerative structures like growth cones and filopodia.

Conclusions:

• Chronic streptozotocin-induced diabetes in rats causes significant ultrastructural changes in autonomic nerves of the alimentary tract.
• These changes, characterized by axonal enlargement and organelle accumulation, suggest a distal axonopathy.
• The presence of regenerative structures alongside dystrophic axons indicates a dynamic process of nerve damage and repair in diabetic autonomic neuropathy.