The microvascular complications of diabetes are caused by a reduction in blood supply to organs. As diabetes progresses, the blood vessels in the body are weakened by the persistent elevation of blood glucose. The weakened vessels accumulate small hemorrhages that slow down the flow of blood. The organs most sensitive to a reduction in perfusion are the eyes, kidneys and nerves. A review study in Clinical Diabetes reported that the extent of microvasculature complications in persons with diabetes is dependent on both the duration and severity of hyperglycemia. Additionally, the U.K. Prospective Diabetes Study found that hypertension compounds the microvasculature complications of diabetes.
Hyperglycemia
High glucose concentrations increase the formation of toxic by-products and reactive oxygen species that damage vessel walls. Additionally, glucose and its by-products in cells increase osmotic pressure, which contributes to vessel injury. Once blood vessels are damaged in organs, less oxygen and nutrients are transported to cells and this leads to the death of cells in the eyes, kidneys and nerves.
Retinopathy
Hyperglycemia-caused retinopathy is the leading cause of blindness in the United States and a review in the journal Clinical Diabetes reported that more than 10,000 cases of blindness each year are attributable to diabetes-caused retinopathy. An article published in Diabetes in Control that reviewed the work of Dr. Michael Brownlee and his team reported that high glucose in cells of vessels in the retina increases the production of the toxic substance methylglyoxal. This molecule damages small blood vessels in the retina and the decrease in oxygen delivery stimulates new vessel growth. The new vessels are already compromised, causing intraretinal bleeding and visual loss.
Nephropathy
Glucose toxicity targets the kidney’s main filtering unit, called the glomerulus. When the filtering function of the glomerulus is compromised by blood vessel injury, proteins that are normally reabsorbed by the glomerulus are excreted in the urine. This condition is called microalbuminuria, which is the first indication of progressive nephropathy in diabetic patients. A study in the Journal of Internal Medicine reported that hypertension, which is present in greater than 80 percent of type 2 diabetics at diagnosis, is the primary factor that exacerbates glucose-caused kidney damage.
Neuropathy
Peripheral neuropathy in diabetics manifests as symptoms of burning, tingling, loss of reflexes and pain in the extremities. It can lead to ulcerations and is the major cause of limb amputation in the developed world. Nerves that participate in controlling digestion, heart rate, bladder function, penile function and defecation may also be compromised, leading to the symptoms of slowed gastric motility, diarrhea, constipation, bladder and erectile dysfunction, and abnormal heart rhythms. A study in the Annals of Internal Medicine stated that nearly 50 percent of diabetics develop one or more neuropathies after having the disease for 25 years.
Treatment
Because hyperglycemia and hypertension are the primary contributors to the development of microvasculature complications in diabetes, it is essential to treat both to reduce the risk of developing microvasculature complications. The American Diabetes Association (ADA) recommends that A1C levels be maintained below 7 percent and blood pressure below 130/80 mmHg. A1C refers to the amount of glucose-modified hemoglobin and is a measurement of the average blood glucose concentration over a two- to three-month time period. The ADA stated in the treatment algorithm for type 2 diabetes published in Diabetes Care that clinical trials and epidemiological studies provide enough evidence that maintaining glycemic control significantly reduces the risk of microvascular complications in diabetics. A review article in Postgraduate Medicine stated that several clinical studies have demonstrated that medications that reduce blood pressure reduce the occurrence of microvasculature complications in diabetics.
References
- Clinical Diabetes: Microvascular and Macrovascular Complications of Diabetes
- Diabetes in Control: Researchers Discover Link between Hyperglycemia and Retinopathy
- Journal of Internal Medicine: Nephropathy in Type 2 Diabetes
- Annals of Internal Medicine: Diabetic Peripheral Neuropathies
- American Diabetes Association: Hypertension
