Streptozotocin-induced Diabetes Causes Crucial Morphological Changes in Abdominal Motoneurons and Muscles of Rats

Naomi Oshiro,Masatoshi Niwa,Ken Muramatsu,Toru Tamaki

doi:10.15344/2455-7498/2018/143

Abstract

Background: Diabetic neuropathy (DN) is a major complication of diabetes. Although it is wellestablished that DN targets sensory and autonomic nerves, little is known about its influence on motor disorders. Methods: This study investigated morphological alterations inabdominal (Abd) motoneurons and muscles of experimental type I diabetic rats. Alterations in the number and size of Abd motoneurons were studied using retrograde labeling techniques in diabetic rats 6 or 14 weeks after injection of streptozotocin (diabetic group). Age-matched control animals were labeled at 6 or 14 weeks after saline injection (control group). Further, the thicknesses of the external oblique, internal oblique, transversus abdominis (TA), and rectus abdominis muscles were similarly examined and the cross-sectional area of the TA myocytes was measured. Results: The number and mean size of cell bodies significantly decreased in Abd motoneurons in the diabetic group compared with the control group (P < 0.05). As diabetes progressed, there was a clear decrease in the number and mean motoneuron size (P < 0.05). In the diabetic group, the thickness of Abd muscles was reduced, as was the cross-sectional area of the TA myocytes (P < 0.05). Moreover, there was a clear decrease in muscle thickness and in the cross-sectional area of the myocytes (P < 0.05). Conclusion: We suggest that hyperglycemia induceda reduction in the number and size of Abd motoneurons and atrophy of Abd muscles at 6 and 14 weeks after induction of diabetes by streptozotocin. Therefore, Abd muscular disorders caused by hyperglycemia may relate to a wide range of disorders, such as those involved with expiratory, defecation function, and trunk movement.

Highlights

Diabetic neuropathy (DN) is symmetric and duration dependent, and involves sensory loss, pain, and distal weakness in the early stage of diabetes [1,2,3]
Abdominal (Abd) muscles consist of the external oblique (EO), internal oblique (IO), transversus abdominis (TA), and rectus abdominis (RA), which are innervated by motoneurons located in the ventral horn of the lower thoracic and upper lumbar spinal cord [9,10]
The number and mean size of cell bodies decreased in Abd motoneurons in the diabetic group

Summary

Introduction

Diabetic neuropathy (DN) is symmetric and duration dependent, and involves sensory loss, pain, and distal weakness in the early stage of diabetes [1,2,3]. In the later stage, muscle weakness spreads through proximal areas, including ankles, knees, and hips, whereas “stocking and glove” sensory losses remain restricted to distal regions [4,5]. These weaknesses correlate highly with the severity of DN[5,6].we recentlyrevealed a significant decrease in the number of labeled gamma motoneurons [7] and a loss of labeled alpha motoneuronsinmedial gastrocnemius (MG) muscles, followed by a later loss of labeled gamma motoneurons in MG muscles using retrograde labeling technique [8]. It is wellestablished that DN targets sensory and autonomic nerves, little is known about its influence on motor disorders

Methods

Results

Discussion

Conclusion