Vascular and neural dysfunction in Zucker diabetic fatty rats: a difficult condition to reverse

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Abstract
Aim:  We had previously demonstrated that vascular and neural dysfunction in Zucker diabetic fatty (ZDF) rats is progressive. In this study, we sought to determine whether monotherapy of ZDF rats can reverse the vascular and nerve defects.Methods:  ZDF rats at 16 weeks of age were treated for 12 weeks with the angiotensin‐converting enzyme inhibitor enalapril, the antioxidant α‐lipoic acid, the HMG‐CoA reductase inhibitor rosuvastatin or the PPARγ agonist rosiglitazone. Vasodilation of epineurial arterioles was measured by videomicroscopy. Endoneurial blood flow (EBF) was measured by hydrogen clearance, and nerve conduction velocity was measured following electrical stimulation of motor or sensory nerves.Results:  Motor nerve conduction velocity (MNCV), sensory nerve conduction velocity (SNCV) (70 and 77% of control, respectively), EBF (64% of control), and vascular relaxation in response to acetylcholine (50% of control) and calcitonin gene‐related peptide (CGRP; 73% of control) are impaired in ZDF rats at 28 weeks of age compared with lean littermate controls. Treatment with enalapril and α‐lipoic acid attenuated the decrease in MNCV and SNCV. Enalapril, α‐lipoic acid and rosiglitazone treatment of ZDF rats were partially effective in improving endothelium‐dependent vascular dysfunction as measured by vascular relaxation in response to acetylcholine. The same drugs also attenuated the decrease in EBF. However, impairment in vascular relaxation in response to CGRP was improved with only α‐lipoic acid or rosuvastatin treatment. The increase in superoxide and nitrotyrosine levels in vascular tissue was attenuated by all treatments.Conclusions:  The efficacy of monotherapy treatment of ZDF rats using different classes of drugs for vascular and neural dysfunction once complications have developed did not achieve expected levels. This could be because of the complex aetiology of vascular and neural disease in type 2 diabetes.

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