The complications of diabetes have traditionally been categorized as micro- or macrovasculature in nature. Individuals with diabetes are at an increased risk of macrovascular complications, including cardiovascular disease and stroke, and also suffer from microvascular disorders including retinopathy, nephropathy and neuropathy. There is increasing evidence these micro- and macrovascular conditions may be linked. Our objective is to determine if direct effects of hyperglycemia on a specific microvascular bed, the vasa vasorum, promotes diabetes-associated accelerated atherosclerosis.
Methods and Results:
The effects of hyperglycemia on retinal and vasa vasorum neovascularization and aortic atherogenesis were examined in streptozotocin-injected apolipoprotein-E deficient (ApoE-/-) mice and normoglycemic ApoE-/- controls. Microvessel densities of the retina and vasa vasorum were quantified at 5, 10, 15 and 20 weeks of age. Atherosclerotic lesion volume in the ascending aorta was determined at the same time points. The expression levels of pro-angiogenic factors, VEGF and VEFGR2, were also determined. Data from normoglycemic ApoE-deficient mice indicate that there is an expansion in vasa vasorum density as the atherosclerotic lesion area increases. In contrast, hyperglycemic ApoE-/- mice have significantly larger atherosclerotic lesions (2 fold, P<0..05) but have no detectible neovascularization of the vasa vasorum A deficiency in VEGF expression in the artery walls of the hyperglycemic mice may explain lack of neovascularization.
These findings indicate that the microvessel structure of the vasa vasorum is altered by hyperglycaemia. The development and progression of atherosclerosis in hyperglycemic ApoE-deficient mice directly correlates with, and may be influenced by, microvascular changes.