Diabetes 51:2619-2628, 2002
© 2002 by the American Diabetes Association, Inc.
Dissection of Metabolic, Vascular, and Nerve Conduction Interrelationships in Experimental Diabetic Neuropathy by Cyclooxygenase Inhibition and Acetyl-L-Carnitine Administration
Rodica Pop-Busui,
Victor Marinescu,
Carol Van Huysen,
Fei Li,
Kelli Sullivan,
Douglas A. Greene,
Dennis Larkin, and
Martin J. Stevens
From the Division of Endocrinology and Metabolism, Department of Internal Medicine, and the Michigan Diabetes Research and Training Center, University of Michigan, and the Ann Arbor Veterans Administration Hospitals, Ann Arbor, Michigan
Alterations in cyclooxygenase (COX) pathway activity have been implicated in the pathogenesis of experimental diabetic neuropathy (EDN). These studies explore the relationships between COX-mediated and acetyl-L-carnitine (ALC)-sensitive defects that contribute to functional, metabolic, and vascular abnormalities of EDN. The effects of nonselective COX inhibition with flurbiprofen were contrasted with selective COX-2 inhibition with meloxicam, administered alone and in combination with ALC in nondiabetic (ND) and streptozotocin-induced diabetic (STZ-D) rats. Flurbiprofen treatment of ND rats replicated many of the biochemical and physiological abnormalities of EDN, i.e., reduced motor nerve conduction velocity (MNCV), total and endoneurial nerve blood flow (NBF), Na,K-ATPase activity, and myo-inositol (MI) and taurine content. In STZ-D rats, however, flurbiprofen paradoxically prevented endoneurial NBF deficits but not MNCV slowing. Coadministration of 50 mg · kg-1 · day-1 ALC prevented reductions in MNCV, Na,K-ATPase activity, and endoneurial NBF in flurbiprofen-treated ND and STZ-D rats. In contrast, selective COX-2 inhibition with meloxicam was without effect on MNCV, NBF, or MI content in ND rats and prevented MNCV slowing and NBF deficits in STZ-D rats. Western blot analysis showed unchanged sciatic nerve COX-1 protein but increased COX-2 protein abundance in STZ-D versus ND rats. These results imply 1) a tonic role of the COX-1 pathway in the regulation of nerve osmolytes and Na,K-ATPase activity and the maintenance of NBF in ND animals and 2) activation of the COX-2 pathway as an important mediator of NBF and MNCV deficits in EDN.

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Copyright © 2002 by the American Diabetes Association.
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