Effect of endurance exercise on myosin heavy chain isoform expression in diabetic rats with peripheral neuropathy.
OBJECTIVE
This study evaluated the effect of endurance exercise on myosin heavy chain (MHC) isoform expression in soleus muscle of diabetic rats with peripheral neuropathy.


METHODS
Male Sprague Dawley rats were randomly divided into four groups: control sedentary, diabetic sedentary, control exercise, and diabetic exercise. The exercised animals performed treadmill running five times per week. After 12 wks, electrophysiologic testing documented peripheral neuropathy in the diabetic rats. The soleus muscles were then excised and quick-frozen. Cross-sections were immunohistochemically stained for slow, fast, developmental, and neonatal MHCs. Fiber-type composition and fiber cross-sectional areas were then determined.


RESULTS
The diabetic groups showed a significantly greater percentage of fast MHC than did the control groups, regardless of exercise status (diabetic sedentary, 22.6%; diabetic exercise, 25.2%; control sedentary, 13.5%; control exercise, 13.1%). The diabetics also showed a significantly lower percentage of slow-only MHC than controls (diabetic sedentary, 77.1%; diabetic exercise, 74.3%; control sedentary, 86.2%; control exercise, 86.1%). No differences in muscle fiber cross-sectional area existed between the groups. The exercised animals showed greater expression of developmental MHC than did the sedentary animals (diabetic sedentary, 1.6%; diabetic exercise, 3.8%; control sedentary, 0.8%; control exercise, 2.0%).


CONCLUSIONS
The altered slow and fast MHC expression in the diabetic muscle is similar to MHC expression in several other conditions, including decreased neuromuscular activity and denervation. Mechanisms of this MHC expression shift are unknown. Chronic endurance training does not alter adult MHC expression in the diabetic animals. The developmental MHC expression is likely a manifestation of uphill treadmill running due to eccentric contractions in the soleus resulting in myofiber injury and regeneration.
Snow
Leann M
LM
Department of Physical Medicine and Rehabilitation, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
Sanchez
Otto A
OA
McLoon
Linda K
LK
Serfass
Robert C
RC
Thompson
Ladora V
LV
D000704:Analysis of Variance; D000818:Animals; D001707:Biopsy, Needle; D003921:Diabetes Mellitus, Experimental; D003929:Diabetic Neuropathies / Q000175:diagnosis / Q000378:metabolism; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D018995:Myosin Heavy Chains / Q000032:analysis / Q000378:metabolism*; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis* / Q000378:metabolism; D010805:Physical Conditioning, Animal; D010807:Physical Endurance / Q000502:physiology*; D011336:Probability; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D013311:Streptozocin
D013311:Streptozocin; D018995:Myosin Heavy Chains