Did you ever hear that diabetes is a disease of blood vessels? Most people think that the definition of diabetes is simply uncontrolled blood sugar, but, in reality, diabetes may be thought of as a vascular disease.
Diabetes can be a very nasty disease affecting most organs in the body. Common problems caused by diabetes include peripheral neuropathy, kidney failure and diabetic retinopathy. The common denominator? Bad blood vessels.
Patients with diabetes can develop peripheral neuropathy. Symptoms of peripheral neuropathy include “pain,” but also numbness of the extremities. Numbness usually begins at the toes and ascends up the legs. At some point the fingers, hands and arms may become involved. The upper extremities (hands and arms) become involved when the numbness has reached a high enough point on the leg so it is now about same distance from the heart as the finger tips. Basically, just remember, when caused by diabetes, peripheral neuropathy begins in the feet.
The problem? The fine, small caliber blood vessels that feed the nerves at the ends of the toes and fingers that give us sensation, eventually fail. Loss of blood supply leads to loss of nerve endings that cause numbness.
Diabetes causes diabetic nephropathy in the kidneys. Here, the fine microvasculature (thin, tiny blood vessels) start to become incompetent and the small filters in the kidney, glomeruli, are unable to properly filter blood and “spill” protein into the urine. Normally, protein, which are rather large molecules, is retained in the blood stream after filtration through the glomeruli in the kidney. Due to damage caused by diabetes, these vascular filters do not work properly, letting protein accumulate in the urine. Long-standing diabetic nephropathy can lead to renal (kidney) failure. Again, small, fine blood vessels are the culprit.
Diabetic retinopathy is a vascular problem as well. As we know, the most common problem in patients with diabetic retinopathy is diabetic macular edema. Macular edema develops when the small retinal blood vessels also “leak” into the surrounding tissue. This can cause decreased vision if it occurs within the macula. The tiny blood vessels become incompetent and start to leak fluid and proteins into the retinal space. Sound familiar?
Diabetic retinopathy can also cause loss of blood supple to the retina. When a tissue has reduced blood supply, or, when a tissue does not receive the proper amount of oxygen (via the blood), the condition is called ischemia. Ischemia arises in the retina when the fine microvasculature of the retina stops to function. It no longer gets sufficient oxygen to the retinal cells. This ischemia is not treatable, can cause loss of vision if it affects the macula and may lead to proliferative diabetic retinopathy.
Researchers have focused attention on pericytes, cells that line the blood vessel walls, as the principal culprit in these “vascular” diseases. Long term exposure to “high sugar” may be related, but indirectly. Clearly, diabetes is associated with damage to the fine microvascular in the body. Whether there is a direct cause-effect relationship between sugar and damage, we have yet to know. Most likely, diabetes causes a cascade of events that can cause, over time, damage to the peripheral nerves, kidney and eyes.
Randall V. Wong, M.D.
Ophthalmologist, Retina Specialist