Two important findings about the powerful antioxidant vitamin E by researchers in the Center for Human Nutrition may provide new therapies in the quest to reduce cardiovascular disease, the main cause of death in type II diabetics. Type II diabetes, also known as non-insulin dependent diabetes mellitus, is the most common form of diabetes. In a study published in Circulation, the researchers found that a high intake of vitamin E can reduce heart disease and stroke risk in type II diabetics.
"This is the first study that shows that vitamin E has anti-inflammatory effects in diabetic patients," said Dr. Ishwarlal Jialal, professor of pathology and internal medicine and senior author of the study. "It could be a further therapy to prevent vascular complications in diabetes since inflammation seems to be critical as a causative factor in diabetic vascular disease," he said.
The findings of a second study published in Free Radical Biology & Medicine showed that this potent antioxidant also reduces the levels of a predictor of cardiovascular disease called C-reactive protein, or CRP. "Vitamin E lowers CRP levels significantly in both diabetics and nondiabetics," said Dr. Jialal. Diabetics, particularly type II are more prone to vascular complications, which can lead to heart attack and stroke. Activity of the pivotal cell termed monocyte, causes plaque to form in the walls of the arteries. This develops into a condition known as atherosclerosis, or hardening of the arteries, which is the leading cause of heart attacks and strokes.
The monocyte is a crucial and readily accessible cell involved in atherogenesis. Data in the earlier study showed that a diabetic monocyte was more active and promoted more inflammation and more free radicals and cytokines, or messenger molecules, than a nondiabetic monocyte. The diabetic monocyte also caused more adhesion to the lining cells of the artery wall. "It was very important to elucidate the pivotal role for inflammation in diabetic vascular disease and examine how it could be modulated," said Dr. Sridevi Devaraj, assistant professor of pathology.
In the Circulation study, type II diabetics with and without macrovascular disease were compared with nondiabetics. Twenty-five participants in each of the three groups were given 1,200 International Units of natural vitamin E (alpha-tocopherol) daily for three months followed by two-months without the supplement. Blood was taken from all the patients at the beginning of the study, after three months and two months after the vitamins were discontinued. The effect of the vitamin E was similar in all three groups. Drs. Jialal and Devaraj found that increased inflammation caused by monocytes was reduced when diabetics were given 1,200 IU per day of vitamin E for three months.
In the second study on the benefits of vitamin E, Drs. Jialal and Devaraj conducted a five-month study on 75 people. The blood tests administered before the vitamin E therapy began showed that diabetic patients, especially those with vascular complications, had increased levels of CRP and interleukin-6. Studies have shown that CRP is an independent risk factor for cardiovascular disease in people with and without diabetes.The study subjects were divided into three groups: those with type II diabetes and heart disease, those with type II diabetes without heart disease, and a normal control group. Each person in each ground was given 1,200 IU of natural vitamin E daily for three months. The researchers measured each person's CRP levels before and after supplementation and two months after the vitamin E therapy had ended. They found that vitamin E supplementation lowered the levels of CRP by 30 percent in all three grounps. Levels of the monocyte interleukin-6, which elicits the secretion of CRP from the liver, were decreased an average of 50 percent in all groups.
"This is another piece of evidence that shows that vitamin E decreases another prototypic marker of inflammation and may thereby contribute to reduction in cardiovascular disease in both diabetics and nondiabetic subjects," Dr. Devaraj said. The American Diabetes foundation funded both studies.
