Benfotiamine reduced collagen IV contents of sciatic nerve in hyperglycemic rats

Abstract

Background: Neuropathy as a common complication of hyperglycemia in diabetic patients is probably caused by metabolic and structural changes in extracellular matrix (ECM) of peripheral nerves. This study was designed to evaluate the effects of benfotiamine (BT) on the structural, biological and mechanical characteristics of rat sciatic nerve in hyperglycemic condition.

Materials and methods: Forty eight adult male Wistar rats were assigned to 6 groups (n = 8): control (healthy rats with no treatment; C), positive control (healthy rats received BT treatment; B), negative control groups 1&2 (hyperglycemic rats kept for 4 and/or 8 weeks; 4WD and 8WD, respectively) and experimental groups 1&2 (hyperglycemic rats treated by daily oral gavage of 100 mg kg^{- 1} body weight BT for 4 and/or 8 weeks; 4WD + BT and 8WD + BT, respectively). Hyperglycemia was induced by a single intraperitoneal injection of of streptozotocin (55 mg kg^{- 1} body weight). After a period of experimental period (4 and/or 8 weeks) rats were sacrificed and from each two segments (1 cm length) of left sciatic nerve were sampled. These samples were prepared for histological examinations (light and electron microscopy), collagen IV immunohistochemistry and strength tensile test.

Results: In comparison to control groups, in 4WD and 8WD groups the amount of type IV collagen was increased, the structure of myelin sheath and nerve fibers were extensively altered and the tensile strength was significantly decreased (p < 0.05) while in 4WD + BT and 8WD + BT groups these abnormalities were attenuated.

Conclusions: It seems that BT treatment may rescue the sciatic nerve from the hyperglycemic-induced ECM structural abnormality. This beneficial advantage of BT is likely exerted through the modification of glucose metabolism pathways.

Keywords: Benfotiamine; Collagen IV; Diabetes; Sciatic nerve; Tensile strength.

Fig. 1

Light microscopy examinations of collagen content of sciatic nerve in different groups. A, control; B, 4WD; C, 8WD; D, 4WD + BT; E, 8WD + BT. Intensities of picrofuchsin stain are higher in 4WD (b) and 8WD (c) than control (a) and benfotiamine treated groups (d and e). Picrofuchsin staining, 400x

Fig. 2

Evaluation of type IV collagen content in the sciatic nerve of different groups, using immunohistochemical technique. A, control; B, 4WD; C, 8WD; D, 4WD + BT; E, 8WD + BT. Intensities of immunostaining are higher in 4WD (b) and 8WD (c) than control (a) and benfotiamine treated groups (d and e). 400x

Fig. 3

The type IV collagen contents in different compartment of sciatic nerve. The type IV collagen contents are remarkable in epineurium and endoneurium. a control; b 8WD; c 8WD + BT (100x)

Fig. 4

Toluidine blue stained photo micrographs of nerve fibers. a Control, b 4WD, c 8WD, d 4WD + BT, e 8WD + BT. The impaired nerve fibers and myelin sheath (black arrows) are more pronounced in B and C than D and E .(400x)

Fig. 5

The ultra-structure of the sciatic nerves. a control; b 4WD; c 8WD; d 4WD + BT; e 8WD + BT. The myelin destruction and demyelination of axons are apparent in b and c. By benfotiamine treatment the degree of demyelination and separation of myelin layers are substantially declined (d and e).(500x)

Fig. 6

Comparison of the results of force-induced displacements (the threshold of nerve lengthening to rupture) in different groups. Data are presented as mean ± standard deviation. *p < 0.05 and **p < 0.01 compared with control (n = 8)

Fig. 7

Comparison of the results of force-induced displacements (the threshold of nerve scaffold lengthening to rupture) in different groups. Data are presented as mean ± standard deviation, (n = 8)

Fig. 8

Comparison the results of strain strength test (the force required for rupture) of sciatic nerve in different groups. Data are presented as mean ± standard deviation. *p < 0.05 and ***p < 0.001 compared with control (n = 8)

Fig. 9

Comparison of the results of strain strength test (the force required for rupture) of decellularized scaffolds of sciatic nerve in different groups. Data are presented as mean ± standard deviation, (n = 8)