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MCAT Prep Quiz of this Current Magazine |
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Biology | Diabetes mellitus can result in both microvascular... |
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| MCAT Prep Quiz 1 |
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Diabetes mellitus can result in both microvascular and macrovascular sequalae. One of the commonly feared complications of diabetes is diabetic retinopathy. The small blood vessels that supply the eye are susceptible to high glucose levels. However, the exact etiology of diabetic retinopathy remains unclear.
Various circulatory derangements have been noted in diabetic patients. Red blood cell aggregation, rigidity, and platelet aggregation are notable examples. These may all contribute to capillary occlusion.
The persistently high glucose level that are present in diabetic patients prompt the body to convert sugars to alcohol via the aldose reductase pathway. The alcohol products are thought to damage pericyte elements in the capillary vasculature of the eye resulting in the loss of autoregulation. Additionally the excess glucose also results in the increased production of diacylglycerol (DAG) which has the ability to activate protein kinase C (PKC). Both processes result in increased vascular permeability and can result in macular edema with associated loss of central vision.
Disease progression leads to capillary occlusion. The lack of oxygen delivery triggers the release of vasoproliferative factors and angiogenesis. The neovasularization that occurs gives rise to small tenuous vessel that grow initially on the retinal surface and eventually grow inward into the retinal scaffold. The new vessels are prone to disruption and can lead to vitreous hemorrhage. Furthermore, the formation of new vessels is also associated with the growth of fibrous tissue. The vitreous can apply traction on the retina via this fibroglial connection and produce a retinal detachment and blindess. |
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