Ann Rehabil Med.  2017 Jun;41(3):402-412. 10.5535/arm.2017.41.3.402.

Effects of Exercise on Neuropathy in Streptozotocin-Induced Diabetic Rats

• Lee EC
• Kim MO
• Roh GH
• Hong SE

• KMID: 2389455
• DOI: http://doi.org/10.5535/arm.2017.41.3.402

Abstract

OBJECTIVE
To evaluate the effects of early regular exercise and to assess the electrophysiological and histopathological findings of the rat tail nerve in relation to the timing of exercise training for swimming exercise in rats with diabetic neuropathy.
METHODS
We used 70 Sprague-Dawley male rats, and the experimental group comprised 60 rats, and the control group comprised 10 rats. Diabetes was induced by intraperitoneal injection of streptozotocin. Blood glucose concentrations were measured in tail vein blood samples. The experimental group was divided into 6 subgroups according to insulin treatment and swimming exercise: group 1, diabetic control; group 2, insulin treated; group 3, insulin untreated with early swimming exercise; group 4, insulin treated and early swimming exercise; group 5, insulin treated and late swimming exercise; and group 6, insulin untreated with late swimming exercise. Sensory and motor nerve conduction studies were performed weekly up to the 13th week using rat tail nerves. The effect on structural diabetic neuropathy was assessed by morphometry and ultrastructural examination of the rat tail nerve fiber at the 14th week.
RESULTS
An exercise effect was observed in the insulin treated groups, but it was not observed in the insulin untreated groups. The sensory nerve conduction study in the rat tail revealed significantly prolonged latency and decreased amplitude in groups 1 and 6, and a further delay was observed in group 5 when compared to group 4. Decreased thickness of myelin was found in groups 1 and 6 through morphometry.
CONCLUSION
Early regular exercise programs in addition to conventional insulin treatment may retard the progression of diabetic peripheral neuropathy.

Keyword

Nerve tissue; Streptozotocin; Diabetic neuropathies; Swimming; Neural conduction

MeSH Terms

Animals
Blood Glucose
Diabetic Neuropathies
Humans
Injections, Intraperitoneal
Insulin
Male
Myelin Sheath
Nerve Fibers
Nerve Tissue
Neural Conduction
Peripheral Nervous System Diseases
Rats*
Rats, Sprague-Dawley
Streptozocin
Swimming
Tail
Veins
Blood Glucose
Insulin
Streptozocin

Figure

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  Fig. 1 Flow chart of the experiment.

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  Fig. 2 (A) Measurements of the orthodromic sensory nerve conduction study. (B) Measurements of the motor nerve conduction study.

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  Fig. 3 (A) An example of sensory nerve action potential of the rat tail nerve. (B) An example of compound muscle action potential of the rat tail nerve. A, amplitude; L, latency.

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  Fig. 4 Effects of insulin and exercise treatment on blood glucose levels. A significant difference was observed between insulin untreated groups and insulin treated groups from the 3rd week (*p<0.05, difference of blood glucose levels between groups 2, 4, 5 and groups 1, 3, 6). Blood glucose level was decreased significantly in the insulin treated groups in comparison with the insulin untreated group. DM, diabetes mellitus; I, insulin treated; EE, early exercise; LE, late exercise.

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  Fig. 5 Effects of insulin and exercise treatment on body weight. A significant difference was observed between the insulin untreated groups and the insulin treated groups from the 4th week (*p<0.05, difference of body weight between groups 2, 4, 5 and groups 1, 3, 6). Body weight was decreased significantly in the insulin untreated groups in comparison with the insulin treated group. DM, diabetes mellitus; I, insulin treated; EE, early exercise; LE, late exercise.

• 

  Fig. 6 (A) Effects of insulin and exercise treatment on sensory nerve latency. A significant difference was observed between the insulin untreated groups and the insulin treated groups from the 5th week (*p<0.05, difference of distal latency in sensory nerve conduction study between groups 2, 4, 5 and groups 1, 3, 6). Sensory nerve latency was decreased significantly in the insulin treated early exercise group in comparison with the other insulin treated group from the 7th week. (B) Effects of insulin and exercise treatment on sensory nerve amplitude. A significant difference was observed between the insulin treated early exercise group and the insulin treated non-exercise group from the 5th week. Sensory nerve amplitude was increased significantly in the insulin treated early exercise group in comparison with the other insulin treated late exercise group from the 7th week (*p<0.05, difference of amplitude in sensory nerve conduction study between groups 2, 4, 5 and groups 1, 3, 6). DM, diabetes mellitus; I, insulin treated; EE, early exercise; LE, late exercise.

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  Fig. 7 (A) Effects of insulin and exercise treatment on motor nerve latency. A significant difference was observed between the insulin untreated groups and the insulin treated groups from the 5th week (*p<0.05, difference of distal latency in motor nerve conduction study between groups 2, 4, 5 and groups 1, 3, 6). No significantly different values were noted in the insulin untreated groups or the insulin treated groups. (B) Effects of insulin and exercise treatment on motor nerve amplitude. A significant difference was observed between the insulin treated with early exercise group and the other groups at the 3rd week and from the 7th to the 9th week (*p<0.05, difference of amplitude in motor nerve conduction study between groups 2, 4, 5 and groups 1, 3, 6). No significant differences were noted from the values in the insulin untreated groups. DM, diabetes mellitus; I, insulin treated; EE, early exercise; LE, late exercise.

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  Fig. 8 Microscopic examination of rat tail nerves (toluidine blue, ×400): (A) normal control, (B) group 1, (C) group 2, (D) group 3, (E) group 4, (F) group 5, and (G) group 6. There was no evidence of demyelination or axonopathy in all groups.

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  Fig. 9 Electron microscopic findings of rat tail nerves (×5,000): (A) control group and (B) group 1. A disproportionately shrunk thin myelin sheath was observed (arrow).

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