Ultrastructural changes of human cardiac atrial nerve endings in diabetes mellitus.
BACKGROUND
Autonomic neuropathy resulting from long-term diabetes mellitus may affect heart innervation. However, so far diabetes induced morphological changes of cardiac nerves are not well-known. In this study human cardiac atrial tissue from diabetic patients was analysed by electron microscopy for structural alterations as a result of diabetic neuropathy.


METHODS
In coronary bypass surgery, an edge of the right auricle was routinely resected for reason of extracorporal circulation. Thin cardiac tissue sections of 100 nm were studied by electron microscopy. Atrial tissue samples were collected from 5 patients with long-standing diabetes (for at least 8 years) and compared to atrial tissue samples from 5 patients without diabetes, equally undergoing coronary bypass surgery.


RESULTS
In all atria-free nerve endings with unmyelinized, axons were observed. Cross sections of 479 axons from diabetic patients were compared to 419 axons of nondiabetic patients. The number of altered axons was significantly higher in cardiac tissue of diabetic patients (32%) in comparison to normal subjects (17%). In diabetic patients, 20% of the intra-axonal mitochondria were condensed or hydropic, whereas in nondiabetic patients only 4% of the mitochondria were altered. Membrane fragments were present in 21% of the axons in atria of diabetic patients compared to 10% in nondiabetic subjects. Only in cardiac axons from diabetic patients there were lamellar bodies, dissolved axoplasma and junctions between neighbouring axons in a minor number. Few vacuoles were present in axons of both groups.


CONCLUSIONS
In myocardial atrial-free nerve fibre bundles of diabetic patients, the amount of degenerative changes was higher in comparison to atrial cardiac tissue from nondiabetic subjects. These morphological alterations may indicate manifestation of diabetic neuropathy and might contribute to the impairment of autonomic neural control affecting the heart in long-standing diabetes mellitus.
Schramm
E
E
Universität Würzburg, Würzburg; Johanniter-Krankenhaus Stendal, Stendal, Germany.
Wagner
M
M
Nellessen
U
U
Inselmann
G
G
D000368:Aged; D001369:Axons / Q000473:pathology / Q000648:ultrastructure; D001026:Coronary Artery Bypass; D003327:Coronary Disease / Q000473:pathology* / Q000601:surgery; D003925:Diabetic Angiopathies / Q000473:pathology* / Q000601:surgery; D003929:Diabetic Neuropathies / Q000473:pathology*; D005260:Female; D006325:Heart Atria / Q000294:innervation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology / Q000648:ultrastructure*; D013564:Sympathetic Nervous System / Q000473:pathology / Q000648:ultrastructure*