Diabetes mellitus remains a leading cause of neurological morbidity (1). In particular, neuropathy affects 60-70% of diabetics and has no effective treatment options. Though the precise mechanisms underlying human diabetic neuropathy are not established, significant research indicates nerve ischemia as a final common pathway. Numerous clinical and experimental studies show impaired vascular endothelial fibrinolysis and antithrombotic regulatory mechanisms, factors inked to diabetes, are important predictors for increased risk of vascular events and ischemic stroke. Furthermore, in vitro studies suggest that key regulatory proteins for both native endothelial fibrinolysis and antithrombotic function may be reduced by metabolic and inflammatory consequences of advanced glycosylation end stage product deposition (AGE's) in blood vessels. Yet, no prior studies have examined whether these same thrombosis regulatory mechanisms are important in the pathogenesis of diabetic neuropathy. Our preliminary data shows that tissue plasminogen activator (tPA) is absent from a substantial proportion of endoneurial vessels in diabetic nerves, but not controls. We also found that thrombomodulin (TM), an endothelial membrane receptor that deactivates thrombin and accelerates activated protein C formation (APC, anti-thrombotic enzyme), is essentially absent in diabetic nerve microvessels, but present in all controls. This biopsy based case-control study tests the hypothesis that key vascular endothelial proteins that regulate fibrinolysis and the TM-Protein C mechanisms are deficient in diabetic nerve microvasculature, constituting a distinct prothrombotic profile compared to non-diabetic control nerves, and that these deficiencies are related to neuropathy severity and the deposition of advanced glycation endproducts; (AGES) in the microvessel wall.
Specific aims are to determine (a) whether tPA and TM expression are reduced and plasminogen activator inhibitor-1 (PAI-1) increased, by immunohistochemistry and in situ hybridization, on epi-, peri-, and endoneurial vessels in the microcirculation of diabetic peripheral nerve compared to age-sex matched non-diabetic controls, (b) whether alterations of tPA, PAI-1 or TM expression in nerve microvessels or plasma are greater in individuals with more severe clinical, electrophysiological and neuropathological rating scores, and or (c) related to AGE deposition on nerve microvasculature. Results of this proposal will establish the requisite mechanistic relationships between AGE-mediated endothelial based prothrombotic changes and clinical diabetic neuropathy severity to better understand hyperglycemia induced nerve injury and develop pharmacological and genetic strategies to reduce morbidity associated with this common disorder.
| Hafer-Macko, Charlene E; Ivey, Frederick M; Sorkin, John D et al. (2007) Microvascular tissue plasminogen activator is reduced in diabetic neuropathy. Neurology 69:268-74 |
| Hafer-Macko, Charlene E; Yu, Shuzhen; Ryan, Alice S et al. (2005) Elevated tumor necrosis factor-alpha in skeletal muscle after stroke. Stroke 36:2021-3 |
| Hafer-Macko, Charlene E; Ivey, Frederick M; Gyure, Kymberly A et al. (2002) Thrombomodulin deficiency in human diabetic nerve microvasculature. Diabetes 51:1957-63 |
| Hafer-Macko, Charlene E; Ivey, Frederick M; Gyure, Kymberly A et al. (2002) Reduced thrombomodulin in human peripheral nerve microvasculature. Muscle Nerve 26:218-24 |
